Gradual low-passivation of infrared detectors of group II-VI.

专利摘要:

公开号:NL8901178A
申请号:NL8901178
申请日:1989-05-11
公开日:2001-06-01
发明作者:
申请人:Santa Barbara Res Ct；
IPC主号:

专利说明:

Short designation: Gradual low-passivation of infrared detectors of group II-VI ..
The invention generally relates to semiconductor devices of group II-VI, and in particular to an HgCdTe infrared photo detector, which has a gradual low-passivation of a composition of group II-VI with a wider prohibition zone, which layer is formed by a cation substitution process.
Mercury cadmium telluride (Hg .. NCd Te, where x ranges from approximately zero (1-x) x to 1.0 and typically has values in the range of 0.2 to 0.4) photo diodes in a typically fabricated as 2-dimensional arrays and comprise a passivation layer deposited on an upper surface of the array, which passivation layer contains low temperature photochemically SiO 2, evaporated ZnS, or anodically grown CdS. Although suitable for certain imaging applications, it has been found that during certain subsequent processing steps associated with the arrangement, such as a high vacuum baking cycle at 100 ° C required for degassing a Dewar vacuum vessel, in which vessel the photodiode arrangement is housed, that such a conventional passivation layer can be disadvantageous. For example, a deterioration has been observed in critical behavioral parameters, such as leakage current, quantum efficiency, noise (especially at low frequencies), spectral i-response and optical zone. This deterioration is particularly evident in long wave detectors, where changes in surface potential approximate the energy of the forbidden zone. Porosity of the passivation layer and lack of adhesion with the HgCdTe surface underneath are also common problems observed with the conventional passivation layers described above.
Furthermore, insofar as these conventional passivation materials form no more than a coating on the HgCdTe surface, control of the energy levels at the HgCdTe / passivation interface is difficult or impossible to achieve. A limitation of such conventional coatings is the fact that it is necessary to both create and maintain flat-band conditions at the HgCdTe / passivation interface if the arrangement is to maintain a desired level of behavioral parameters, especially during and after high temperature processing and storage.
The aforementioned problems are overcome and other advantages are realized by an IR photodiode and an arrangement thereof constructed in accordance with the invention. Accordingly, the invention discloses a method of forming a passivation region on a semiconductor device, wherein: - a body consisting of Group II-VI material, which has a characteristic energy or energies in the forbidden zone, is started from; - prepares a surface area of the body; - forms a layer consisting of atoms of group II, which layer overlies the prepared surface of the body; and - forms a passivation region within the prepared surface region, the atoms of Group II occupying cation sites in gradually decreasing concentration as a function of the depth in the surface region. The surface may have been prepared by a surface etching process which makes the surface region of Group II atoms leaner, resulting in cation-vacant sites that have a gradually decreasing concentration as a function of depth within the surface region.
As a result, the Group II atoms occupying these cation sites also have a gradually decreasing concentration as a function of depth.
According to the invention, the step of starting from a body of Group II-VI material can be performed by starting from a body of Hg, CD Te, Hg. .Zn Te or HgCdZnTe, and one step ahead
V J. —X / X ^ 1 “Χ / X
Layering is performed by forming a layer consisting of Cd, Zn, CdTe, ZnTe or HgCdTe or HgZnTe with a wider energy band in the forbidden zone of the characteristic energy or energies occurring in the forbidden zone.
The passivation region can be formed by annealing the body and the overlying layer in a saturated mercury atmosphere.
These and other aspects of the invention will be made more apparent in the following detailed description of preferred embodiments, which are discussed with reference to the accompanying drawings.
Fig. 1a is a stylized perspective view, not to scale, of a portion of an arrangement 1 of photo-diodes 2 of group II-VI, which according to the invention have a passivation layer 5 with a gradual composition, consisting of material of group II-VI; Fig. 1b is a cross-sectional view of a photo-diode 10 having a HgCdTe radiation absorbing base layer 12, a HgCdTe cap layer 14 and a layer 16 with gradual passivation; Fig. 2 is a representative energy diagram of the forbidden zone of the CdTe or CdZnTe passivated photo-diode of Fig. 1b; Figures 3a-3f show various steps of a method according to the invention for manufacturing a layer with gradual passivation on a photo-diode; Figures 4a-4d are representative cross-sectional views of an depleted HgCdTe layer showing the cation substitution of the Group II atoms within the depleted surface; Figure 5 is a graph showing the Cd concentration against depth as a function of the annealing time at 400 ° C in saturated mercury vapor; Figures 6a and 6b show a comparison of I-V curve for a diode passivated in accordance with the invention and for a conventional SiO 2 passivated LWIR photo diode, respectively; and Figures 7a and 7b show a comparison of RqA as a function of the storage time at 100 ° C for a gradual layer of CdTe and conventional SiO1, LWIR 5X5 arrangement, respectively. insulated diodes with variable zc Although the invention will be described in the context of a mesa-type photoelectric radiation detector with exposed back, it should be realized that the insights of the invention also apply to photoconductive radiation detectors with exposed front. The invention is also applicable to homo-reverse and hetero-reverse devices as well as devices of the planar type, wherein a base layer of a given conductivity type has regions or "pits" of an opposite conductivity type formed in an open surface thereof . As will be appreciated, the invention also includes surface passivation of devices other than photodiodes, such as other dipole devices, and also CCD and MIS devices, which contain a region of the Group II-VI semiconductor material from which the material is largely exists.
Referring primarily to Figure 1a, it shows a stylized perspective perspective view of a portion of an array 1 of photodiodes 2, the view being not to scale. The photo-diodes are formed from a Group II-VI material such as Hg (i ^ Cd ^ Te, Hg ^ j ^ Zn ^ Te or HgCdZnTe. The material is distinguished into material which is of a first conductivity type and material which is of a second conductivity type for forming a plurality of diode reversals The array 1 can be viewed as consisting of a plurality of photodiodes 2 arranged in a regular 2-dimensional array. which may be long wave, medium wave or short wave (LWIR, MWIR or SWIR) radiation incident on a surface of the arrangement 1. The arrangement 1, in an illustrative embodiment of the invention, contains a radiation absorbing base layer 3 of Hg ^ ^ Cd ^ Te ^ a - * - ^ 8 conductor material, where the value of x determines the responsiveness of the arrangement on either LWIR, MWIR or SWIR Each of the photo-diodes 2 is defined by a mesa structure 6, which is typically formed doo etching each other's intersecting V-shaped grooves in the base layer via an overlying cap layer, which is of the opposite conductivity type compared to the base layer. Each of the photo diodes 2 includes a zone of contact metallization 4 on an upper surface thereof, the metallization serving to electrically couple an underlying photo diode to a reader (not shown), typically via a (not -shown) indium bump (non-addressable auxiliary memory). The top surface of the arrangement 1 is also provided, in accordance with the invention, with a passivation layer 5 consisting of a layer of Group II-VI material, which has a gradual composition as a function of depth.
Referring now to Fig. 1b, there is shown in section, one of the photo-diodes of the arrangement 1, in particular a double layer of HgCdTe hetero-reverse photo-diode 10 with a bottom surface for admitting infrared radiation. Photo-diode 10 includes a base layer 12 in which the incident radiation is absorbed, thereby generating charge carriers. The radiation absorbing base layer 12 can be either p-type or n-type semiconductor material, and has a cap layer 14, which is of the opposite conductivity type, to form a pn turnable 15. Thus, if the radiation absorbing base layer 12 is of the p-type HgCdTe, the cap layer 14 is of the n-type HgCdTe. Charge carriers generated by the absorption of infrared radiation result in a current flowing over the reverse layer 15, which flowing current is detected by a readout circuit (not shown) coupled to the photo-diode 10.
For example, the base layer 12 may be of the p-type and may be doped with arsenic at a concentration of about 5x10 to about 5x10 3 atoms / cm. The cap layer 14 can be made of the n-type by doping the material with indium in a concentration of about 10 to about 17 3 atoms / cm.
In accordance with the preferred embodiment of the invention, the top surfaces of the Hg ^ ^ Cd ^ Te base layer 12 and cap layer 14 are passivated by giving the chemical composition a gradual gradient, or x value perpendicular to the surface; wherein the chemical composition gradually progresses from that of the active detector material to a larger x value sufficient to create a wider area in the forbidden zone and to generate a reflective barrier for both electrons and holes. Such a layer 16 with gradual passivation functions advantageously to electrically separate the active detector material from the device surface. For example, photo detectors having a cutoff wavelength of about 12 microns can have an x value of about 0.2, which has a gradual gradient, in accordance with the invention, up to an x value of about 0.5 x 1, 0 on the outer surface of the passivation layer.
In accordance with a preferred method of the invention, the gradual passivation in the layer 16 is carried out by a cation substitution method, whereby atoms in a group II substance, such as Cd or Zn, become diffuse at high temperature in the surface of an underlying material in group II-VI. The underlying material may contain HgCdTe. The diffused atoms occupy cation sites previously occupied by Hg and / or Cd atoms. Improved device performance and stability are achieved because the pn diode barrier 15, and an associated diode barrier depletion region, are buried beneath the progressively extending passivation layer 16 and are electrically insulated from surface disturbances and impurities that would otherwise cause diode behavior. decline.
It will be appreciated that the region of the gradual passivation layer 16 forms a hetero-structure with the underlying detector material. That is, the crystalline structure of the passivation layer 16 is substantially continuous with the crystalline structure of the radiation absorbing layers. This crystalline continuity advantageously allows for a continuous extension of the forbidden zone structure of the HgCdTe layers 12 and 14, which have typical energies from 0.1 to 0.3 eV, to the wider forbidden zone of the layer 16 with gradual gradient passivation. The HgCdTe layers 12 and 14 may have similar or completely different forbidden energy zones smaller than those of the layer 16.
For example, CdTe has a prohibited zone of approximately 1.6 eV. This results in a kink of the conduction band in an upward direction, driving electrons back from the HgCdTe / CdTe interface.
This wider forbidden zone further results in the valence band buckling downward, forcing holes out of the interface. This is shown in Figure 2 and will be described in more detail below.
Referring again to Fig. 1b, diode 10 may also include a top layer of glass 18, which may be any suitable dielectric material such as SiN, SiO or ZnS. The contact 20 may consist of 3 4 2 any suitable material effective to form an ohmic contact with the cap layer 14. Preferably, the metallic contact 20 does not appreciably diffuse into the cap layer 14. Metals suitable for forming of the contact 20 are palladium and titanium.
Referring now to FIG. 2, there is shown an idealized energy band diagram of the photodiode 10 of FIG. 1, wherein the broader forbidden zone passivation layer 16 consists of CdTe and wherein the narrower forbidden zone material is either the HgCdTe base layer 12 or the HgCdTe. cap layer 14. As can be seen, a continuously varying potential energy is displayed in the guide wall and valence band so that the conduction band is bent up and the valence band bent down. This results in the repulsion of both electrons and holes from the HgCdTe / gradual passivation interface. This repulsion of both electrons and holes from the interface, whereby the relatively high density of lattice dislocations and impurities would otherwise cause excessive surface state generation currents and a reduced life of the charge carriers, results in the photo-diode of the invention being superior behavior towards conventional SiC2 passivated photo diodes.
Furthermore, the top surface of the layer 16 can be doped with gradual passivation to allow charges on the e.g.
Isolate CdTe surface from the underlying HgCdTe surface.
In the diagram of Fig. 2, the top surface of the CdTe passivation layer 16 is doped with an n-type impurity. If desired, a p-type impurity can be used instead.
A typical dopant concentration of the top surface of the 17 passivation layer 16 is about 10 atoms / cm.
Referring now to Figures 3a-3f, a preferred method of manufacturing a hetero-junction passivation is illustrated. Although Figures 3a-3f illustrate this preferred method in relation to a mesa-type photo-diode, it will be appreciated that the method of the invention is equally applicable to planar-type HgCdTe photo-diodes and their arrangements.
Fig. 3a shows a cross-sectional view of a bilayer HgCdTe hetero junction structure 30, provided with a HgCdTe base layer 32 and a HgCdTe cap layer 34. Base and cap layers 32 and 34 can each be doped with an appropriate impurity such that the one layer of the p-type and the other layer is of the n-type semiconductor material, or may be made of the n-type or p-type by any suitable known method.
Fig. 3b shows the structure of FIG. 3a after mesass 36 are etched to isolate individual diodes, each mesa defining a photo diode. The knife axis 36 can be created using conventional photolithography and etching techniques. Subsequently, a surface preparation operation is effected. In accordance with a method of the invention, the surface preparation operation comprises a surface etching process, which selectively removes both Cd and Hg from the exposed surface regions of the HgCdTe material, thereby depleting the surface region to Group II atoms. This surface etching process is described in more detail below. A layer of source material 38 is then applied to the exterior surface of the blade shaft 36 and exposed portions of the radiation absorbing base layer 32.
This layer of source material is shown in Figure 3c. In Fig. 3d, it can be seen that portions of the source material layer 38 are then removed to define areas where contact metallization will be deposited later. In accordance with an embodiment of the invention, the source material layer 38 consists of CdTe, which is applied by a thermal evaporation process. It will be understood, however, that any suitable deposition process can be used to deposit the layer 38. The layer 38 may also contain something other than CdTe. For example, the layer 38 may contain elemental Cd, elemental Zn, a zinc alloy such as ZnTe, HgCeTe or HgZnTe, which has a broader forbidden energy zone than the underlying material on any suitable Group II material, which has a valency of +2.
Fig. 3e shows the photo-diode structure 30 after a heating process which causes the Cd to diffuse from the layer 38 of source material into the Hg ^ ^ Cd ^ Te base layer 32, respectively. cap layer 34. This heating process also results in a corresponding diffusion of Hg in an opposite direction. This inward diffusion of Cd causes the composition, or x value, to gradually progress from about x = 1.0 on the outer surface of the layer 38 to that of the value x of the HgCdTe, which contains the base layer 32 or cap layer 34. . This diffused layer, or gradual area, is shown schematically in FIG.
3rd as a number of perpendiculars 39 on the surface.
In Fig. 3f, a complete portion of the photo-diode array is shown after applying contact metallization 40 to the individual photo-diodes. Fig. 3f also shows the optical top layer of glass 42.
Referring to Figures 4a-4d, there is illustrated a surface region depleted in Hg and Cd, while also illustrating the inward diffusion of Cd or Zn during a cation substitution process. The mechanism that effects the gradual composition composition of the surface region is related to the diffusion of Cd atoms from the source layer 36 to the underlying HgCdTe surface, in which the Cd atoms near the surface occupy cation sites previously occupied by Hg and Cd atoms. This cation substitution process takes place at higher temperatures due to the thermal instability of the Hg-Te bond. Once the Hg-Te bond is broken by thermal activation, an inwardly diffusing Cd atom can be bonded to the Te atom. As an increasing number of cation sites are occupied with Cd atoms, the x value of the HgCdTe base surface and cap layer surface increases. The resulting gradual profile is thus a direct function of the Cd diffusion profile. As a result, the forbidden energy zone of the gradual area increases, while also improving the chemical and thermal stability of this area.
The Hg and Cd atoms can be removed from the upper surface region during the aforementioned surface etching process, which can employ a solution of bromine and ethylene glycol, the bromine concentration typically being 0.25% by volume. The etching solution can be left in contact with the surface for about 1 to 2 minutes. As can be seen in Figure 4a, the surface area of the HgCdTe mass is thereby depleted in both Hg and Cd, the amount of depletion being a function of the depth in the material of the mass. As can be seen in Figure 4b, the source layer 36 is deposited over the depleted upper surface area. The exterior portion of the top surface is typically contaminated by an oxide and / or hydrocarbon layer. This contaminated layer can have a depth of approximately 100 A.E. Beneath this contaminated surface layer is the depleted layer in which a number of vacant cation sites are available, which sites, in accordance with the invention, are filled by, e.g., CD atoms, which diffuse inwardly from the source layer 36 for an annealing process.
During this annealing, some Hg atoms, which diffuse outwards from the mass material, can also enter the Cd-rich layer. Due to the substantial difference between the bonding energies of the Cd-Te and Hg-Te bonds, these Hg atoms do not bind or remain bound to the Te due to the higher temperature used during annealing. Thus, these Hg atoms do not significantly contribute to the composition of this layer, which is consequently enriched with Cd. This Cd enriched layer, as mentioned, progresses compositionally as a function of depth and also has a wider forbidden energy zone than the underlying HgCdTe mass material. The layer enriched with Cd can have a depth of about several hundred A.E. up to several thousands of A.E .; where 5000 A.E. is a typical value depending on the surface preparation process and the annealing time and temperature. It will be appreciated that the inwardly diffusing Cd atoms fill the cation vacant sites created by the surface preparation process, within a region of about 100 A.E. thickness, and also diffuse inward to much greater depths. These Cd atoms replace Hg atoms to create a compositionally progressive region of several thousands of A.E. thickness. As such, approximately a thousand molecular layers of HgCdTe can exist within the enriched region, the layers closer to the surface being richer in Cd than the layers closer to the bulk material, in part due to the depletion profile created during the surface etching process. Thus, this enriched layer has a gradual composition composition such that the value of x is highest at the top surface of the enriched layer and gradually approaches the value x of the underlying mass material.
The preparation of the top surface region can cause depletion of group II atoms or not. In one embodiment of the invention, the surface is prepared to be stoichiometric (i.e., there is no depletion of Cd or Hg). This stoichiometric surface area is then annealed such that Hg atoms released from the structure due to thermal effects are replaced by Cd atoms. This surface preparation and subsequent annealing causes the forbidden zone on the outer surface to be broadened by cation substitution. This substitution takes place as follows: at 400 ° C (in a saturated Hg atmosphere), the thermal energy is sufficient to break the Hg-Te bonds, releasing Hg atoms in the HgCdTe crystal lattice. Next, Cd atoms diffusing into the HgCdTe from the parent Cd source material are combined with the Te atoms to form the more thermally stable Cd-Te bonds.
Fig. 4c shows an analog structure for the ternary connection
Hg,, Zn Te, wherein Zn is diffused inwardly from (1-x) x source layer 36 to occupy vacant cation sites made available by the aforementioned surface etching and diffusion process.
As can be appreciated, the wider Prohibited Zone Cd-rich layer also serves to isolate the underlying HgCdTe material from the contaminated surface layer, thereby favorably reducing surface recombination and leakage current effects. That is, charge carriers within the underlying HgCdTe are driven back away from the contaminated surface by the Cd-rich layer with wider prohibition zone. Thus, the method of the invention can be advantageously used during the manufacture of various types of photodetecting devices, other types of bipolar reverse devices, charge coupled devices (CCDs) and also metal insulator semiconductor (MIS) devices, like MIS capacitors. The invention can also be advantageously used for the manufacture of photoconductors reacting to infrared radiation.
As shown in Fig. 4d, the method according to the invention can be used to create a layer with gradual passivation and wider forbidden energy zone, which has a quaternary composition. That is, the underlying bulk material can be HgCdTe, while the source layer 36 can be Zn or ZnTe. Thus, the resulting composition of the passivation layer is the quaternary alloy HgCdZnTe. On the other hand, it can leave bulk material. HgZnTe, while the source layer may contain Cd.
In accordance with a preferred method of the invention, the structure 30 of Figure 3 is first annealed at about 400 ° C for about 4 hours in a collected Hg vapor atmosphere to achieve the desired profile of the gradual passivation course. This first annealing is followed by a second annealing at about 250 ° C for about 4 hours on a stoichiometric amount of Hg in the absorbent region of the auxiliary material.
These annealing steps are typically performed in an ampoule, with partial Hg pressure.
In Figure 5, the experimentally measured Cd concentration versus depth is shown as the function of the annealing time at 400 ° C in a collected Hg vapor. As can be seen, the Cd concentration varies in a manner perpendicular to the surface and has a gradually decreasing concentration.
Figures 6a and 6b show a comparison of I-V curves, for diodes, which are passivated in accordance with the invention, respectively. for conventional SiO2 passivated LWIR photodiodes, both of which are fabricated from the same wafer of HgCdTe.
Fig. 7a and 7b show a comparison of RqA as a function of storage time at 100 ° C for a graded layer of CdTe and conventionally SiO 2 passivated LWIR 5x5 arrangement, respectively. insulated diodes with variable surface.
In both Figures 6 and 7, it can easily be seen that infrared photodiodes constructed in accordance with the invention have superior behavioral properties compared to photodiodes constructed in accordance with a conventional SiO 2 passivation layer.
As mentioned previously, presently preferred embodiments of the invention are described herein. It is possible for those skilled in the art to devise changes to these preferred embodiments based on the foregoing description. For example, although the presently preferred embodiments of the invention have been disclosed in the context of a mesa-type arrangement of photodiodes, it is to be understood that the insights of the invention also apply to planar-type photodiodes , and generally on all devices, such as photoconductors, CCDs or MIS devices consisting of Group II-VI material. Thus, it is to be understood that the invention is not limited to only the preferred embodiments as disclosed above, but is instead intended to be limited only as defined by the appended claims.

权利要求:
Claims (50)
[1]
Method for forming a passivation region on a semiconductor device, in which: - a body consisting of material of group II-VI is started from, which in the forbidden zone has a characteristic energy or energies; - prepares a surface area of the body; - forms a layer consisting of atoms of group II, which layer overlies the prepared surface of the body; and - forms a passivation region within the prepared surface region, the atoms of Group II occupying cation sites in gradually decreasing concentration as a function of the depth in the surface region.
[2]
The method of claim I, wherein the step of providing a body of Group II-VI material is accomplished by providing a body of Hg, .Cd Te, Hg, .Zn Te, or HgCdZnTe. II-x7 x II-x7 ^
[3]
The method of claim 1, wherein the step of forming a layer is accomplished by forming a layer consisting of Cd, Zn, CdTe, ZnTe, or HgCdTe or HgZnTe with a wider forbidden energy zone than the characteristic forbidden zone energy or energies of the body.
[4]
The method of claim 3 and further comprising an operation to reverse an upper surface of the passivation area.
[5]
The method of claim 1, wherein the passivation region forming operation comprises an annealing operation of the body at a predetermined temperature for a predetermined time interval.
[6]
The method of claim 5, wherein the annealing operation is effected at about 400 ° C for about 4 hours in a saturated Hg vapor atmosphere.
[7]
The method of claim 6, wherein the annealing operation comprises a further annealing operation at about 250 ° C for about 4 hours.
[8]
The method of claim I and further comprising an operation of forming a layer of a dielectric material over a surface of the passivation region.
[9]
A method of forming a passivation region on a semiconductor device comprising the steps of: - providing a body consisting of Group II-VI material having a characteristic forbidden energy or energy zone; an upper surface region of the body is depleted of group II atoms to form cation-vacant sites therein; - a layer is formed consisting of group II atoms, overlying the depleted region; and - a passivation region is formed at least within the upper surface region of the body, while the group II atoms occupy the cation vacant sites in gradually decreasing concentration as a function of the depth in the region.
[10]
The method of claim 9, wherein the act of producing a body of Group II-VI material is provided by providing a body of Hg., CD Te, Hg. .Zn Te or HgCdZnTe.
[11]
The method of claim 9, wherein the layer forming operation is accomplished by forming a layer consisting of Cd, Zn, CdTe, ZnTe or HgCdTe or HgZnTe with a wider forbidden energy zone than the characteristic forbidden energy or energies zone of the body.
[12]
The method of claim 9 and further comprising a doping operation of an upper surface of the passivating region.
[13]
The method of claim 9, wherein the passivation region forming operation comprises an annealing operation of the body at a predetermined temperature during a predetermined time interval.
[14]
The method of claim 13, wherein the annealing operation is effected at about 400 ° C for about 4 hours in a saturated Hg vapor atmosphere.
[15]
The method of claim 14, wherein the annealing operation comprises a further annealing operation at about 250 ° C for about 4 hours.
[16]
The method of claim 9, further comprising an act of forming a layer consisting of a dielectric material over a surface of the passivation region.
[17]
The method of claim 9, wherein the exhausting operation is accomplished by etching a surface of the body.
[18]
The method of claim 17, wherein the surface is etched with a bromine solution.
[19]
Arrangement of photodiodes reacting to infrared radiation, manufactured by a process, comprising the following operations: - providing a radiation absorption layer with a surface for admitting infrared radiation for generating charge carriers from absorbed infrared radiation, which radiation-absorbing layer consists of a material of group II-VI of the first electrical conductivity type; forming a plurality of regions in contact with the layer, said regions containing a Group II-VI material which is of the opposite electrical conductivity type from the layer to form a plurality of pn diode reverse layers therewith at the interface between the layer and each of the areas; - preparing surface areas of at least exposed surfaces of the p-n diode reverse layers; and - forming a passivation region within the prepared surface regions, the passivation region consisting of Group IV atoms diffused into the prepared surface regions, the Group II atoms occupying cation sites in decreasing concentration as a function of depth in the prepared surface areas; and wherein - the radiation absorbing layer and the number of areas are a first forbidden energy zone, respectively. have a second forbidden energy zone, and the passivation area has a third forbidden energy zone, which is wider than any of the first or the second forbidden energy zone.
[20]
The arrangement of photodiodes produced by the method of claim 19, wherein the radiation absorbing layer and the number of regions are HgCdTe and the cation sites are occupied by cadmium atoms with a gradually decreasing concentration profile as a function of depth in the prepared surface regions.
[21]
The arrangement of photodiodes made by the method of claim 19, wherein the radiation absorbing layer and the number of regions are HgCdTe and the cation sites are occupied by zinc atoms with a gradually decreasing concentration profile as a function of depth in the prepared surface area.
[22]
The arrangement of photodiodes made by the method of claim 19, wherein the radiation absorbing layer and each of the plurality of regions are HgZnTe and the cation sites are occupied by cadmium atoms with a gradually decreasing concentration profile as a function of the depth in the prepared surface areas.
[23]
The arrangement of photodiodes made by the method of claim 19, wherein the radiation absorbing layer and each of the regions consist of HgZnTe and wherein the cation sites are occupied by zinc atoms with a gradually decreasing concentration profile as a function of depth in the prepared surface regions.
[24]
The arrangement of photodiodes made by the method of claim 19, wherein an upper surface of the passivation region is doped.
[25]
A method of manufacturing an array of infrared photodiodes, comprising the following operations: - providing an infrared radiation absorbing base layer and a plurality of areas in contact with the base layer, the base layer and each of the areas consisting of Group II material -VI and which are of the electrically opposite conductivity type, alternately, for defining at an interface between a plurality of pn diode turns, the base layer having a first characteristic forbidden energy zone and the regions having a second characteristic forbidden energy zone; - preparing an upper surface area of at least each of the p-n diode turns; depositing a layer consisting of a group XI material over the prepared surface areas; and - annealing the deposited layer and the underlying Group II-VI material at a first predetermined temperature during a first predetermined time interval such that group II atoms of the deposited layer diffuse into the underlying prepared surface regions, while the group II atoms react with group VI atoms to form a passivation region with a broader forbidden energy band than the underlying material of group II-VI.
[26]
The method according to claim 25, wherein the radiation absorbing layer and the regions consist of HgCdTe and wherein the passivation region contains an region enriched with cadmium atoms with a gradually decreasing concentration profile as a function of the depth in the surface of each of the pn diode retaining layers. .
[27]
The method of claim 25, wherein the radiation absorbing layer and the regions consist of HgCdTe and wherein the passivation region contains an region enriched with zinc atoms with a gradually decreasing concentration profile as a function of the depth in the surface of each of the p-n diode turns.
[28]
The method of claim 25, wherein the radiation absorbing layer and each of the regions are comprised of HgZnTe and wherein the passivation region contains an region enriched with cadmium atoms with a gradually decreasing concentration profile as a function of the depth in the surface of each der pn diode reverse layers.
[29]
The method of claim 25, wherein the radiation absorbing layer and each of the regions are composed of HgZnTe and wherein the passivation region contains an region enriched with zinc atoms with a gradually decreasing concentration profile as a function of the depth in the surface of each of the pn diode reversals.
[30]
The method of claim 25, wherein the radiation absorbing base layer and each of the regions are comprised of Hg. , Cd Te and wherein the U xJ x deposited layer consists of Cd.
[31]
The method of claim 30, wherein the passivation area is a gradual area consisting of Hg ^^^ Cd ^ Te with a value of x equal to about 0.5 to about 1.0 at an upper surface thereof, while the value of x progresses gradually in a direction perpendicular to the surface, such that the value of x at a predetermined depth is approximately equal to the value of x of the underlying base layer and regions.
[32]
A method according to claim 25, characterized in that the radiation absorbing base layer and each of the regions consist of Hg ^ Zn ^ Te and wherein the deposited layer consists of Zn.
[33]
The method of claim 32, wherein the passivation region is a gradual region consisting of Hg ^ Zn ^ Te with an x value equal to about 0.5 to about 1.0 on an upper surface thereof, the value of x gradually progresses in a direction perpendicular to the surface such that the value of x at a predetermined depth is approximately equal to the value of x of the underlying base layer and regions.
[34]
The method of claim 25, wherein the annealing operation is performed at a temperature of about 400 ° C for about 4 hours in an ampoule containing partial Hg pressure.
[35]
The method of claim 34, wherein the annealing operation includes an additional annealing operation at a temperature of about 250 ° C for about 4 hours in an ampoule containing partial Hg pressure.
[36]
The method of claim 25, further comprising the act of doping the top surface of the passivation region.
[37]
The method of claim 25, wherein the preparation operation is accomplished by etching the surface.
[38]
The method of claim 37, wherein the surface is etched with a bromine solution.
[39]
The method of claim 25, wherein the radiation absorbing base layer and each of the regions consist of HgCdZnTe and wherein the deposited layer consists of Zn.
[40]
The method of claim 25, wherein the radiation absorbing base layer and each of the regions consist of HgCdZnTe and wherein the deposited layer consists of Cd.
[41]
A method for passivating a surface of a body consisting of Group II-VI material, comprising the following steps: - providing the body of Group II-VI material; depleting a surface region to be passivated to group II atoms to create vacant cation sites therein; - depositing a layer consisting of group II atoms over the depleted surface area; and - annealing the body and layer at a given temperature for a given period of time, such that the group II atoms within the layer diffuse into the depleted surface region and substitute in the vacant cation sites therein, creating a forbidden energy zone of the surface region increases and the surface is passivated.
[42]
The method of claim 41, wherein the depletion operation creates vacant cation sites in gradually decreasing numbers as a function of depth from the surface.
[43]
The method of claim 42, wherein the passivated surface contains group of atoms II in gradually decreasing concentration as a function of depth from the surface.
[44]
The method of claim 42, wherein the depletion operation is accomplished by etching the surface with a bromine solution.
[45]
The method of claim 41 further comprising a doping step of the passivated surface.
[46]
The method of claim 41, wherein the act of providing a body of Group II-VI material is accomplished by providing an array of photodiodes responsive to infrared radiation.
[47]
The method of claim 41, wherein the act of providing a body of Group II-VI material is accomplished by providing an array of infrared radiation responsive photoconductors.
[48]
48. A method of passivating a surface of a body consisting of Group II-VI material, comprising the following operation: - providing a body of Group II-VI material of substantially stoichiometric composition; depositing a layer consisting of group II atoms over a surface of the body; and - annealing the body and layer, such that Group II atoms from the layer occupy vacant cation sites within the body, the vacant cation sites being created at least by thermal effects caused by the annealing operation.
[49]
The method of claim 48, wherein the annealing operation creates vacant cation sites in gradually decreasing numbers as a function of depth from the surface.
[50]
The method of claim 48, further comprising a doping operation of the passivated surface.

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同族专利:

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公开号 | 公开日

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DE3915321C1|2000-12-28|

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NL195050C|2003-06-27|

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FR2872345A1|2005-12-30|

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GB8910337D0|2002-05-22|

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GB2372375B|2003-01-15|

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GB2372375A|2002-08-21|

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US5880510A|1999-03-09|

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法律状态:
2001-06-01| A1C| A request for examination has been filed|

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2003-09-01| NP1| Not automatically granted patents|

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2008-02-01| V1| Lapsed because of non-payment of the annual fee|Effective date: 20071201 |

优先权:

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申请号 | 申请日 | 专利标题

---

US07/193,029|US5880510A|1988-05-11|1988-05-11|Graded layer passivation of group II-VI infrared photodetectors|

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US19302988|1988-05-11|

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