For MOVPE growth of CdTe on to (100) GaAs the orientation of the epitaxial layer is dependent on a combination of the growth conditions and substrate treatment prior to growth, (100) being the preferred orientation. (111) oriented CdTe layers can be grown on to (111) GaAs substrates. The effect of orientation on the choice of buffer composition, electrical properties and the extent of Ga diffusion from the substrate is discussed. Epitaxial CMT layers grown on to suitably buffered GaAs substrates are compared to similar layers grown on to CdTe substrates.

Close-spaced isothermal vapor phase epitaxy (VPE) was used to grow quaternary Hg1−x−yCdxZnyTe epillayers on Cd1−zZnzTe substrates. Composition, resistivity, and carrier concentration depth profiles were determined in the epilayers. p-n junctions were produced from material with appropriate properties using the Hg diffusion method. The junctions showed excellent I-V characteristics and high spectral detectivities.

HgTe-CdTe superlattices have been grown, for the first time, by photoassisted MOCVD. The substrate temperature was 182°C. Superlattices were obtained despite low growth rates requiring long growth times (∼10 hours). Interdiffusion during growth may be slowed down by growing under saturated Hg vapor to minimize cation-vacancy formation. The nominal superlattice structures were 70Å HgTe-30Å CdTe, 40Å HgTe-40Å CdTe, and similar. Actual superlattice structures were verified by cross-sectional TEM and diffractometer x-ray diffraction patterns. The x-ray diffraction patterns showed satellite peaks up to third order. The actual structures had HgTe layers ∼20% thicker than the nominal (target) values. A grid-like array of dislocations at the substrate-epilayer interface, suggesting operation of a dislocation-blocking mechanism, was observed. Deficiencies in the superlattice growths include a low growth rate, nonuniform layers, high dislocation density (∼108 cm−2 in best layers), and high n-type carrier concentration (∼1018 cm−3 with mobilities up to 3.5 × 104 cm2 V−1 s−1 in the best layer) which may reflect the presence of donor impurities in the material.

The growth of thin films of mercury-based materials by molecular beam epitaxy (MBE) presents significant experimental problems which must be overcome in order to successfully grow infrared detector materials such as mercury cadmium telluride (MCT). Many of the problems associated with the use of Hg in MBE arise from its high room temperature vapor pressure (2 mTorr) and its low sticking coefficient. The MBE system must be designed for Hg usage by considering such things as the ultra high vacuum pumping system, the Hg source, Hg containment, and Hg removal. In addition, Hg is a toxic heavy metal and must be handled appropriately. Other problems involved with the growth of MCT are associated with the design of the MBE furnaces which are used to evaporate cadmium telluride and tellurium.

InSb has served as an important mid-wave IR (λ=3−5μm) detector material for several decades. In this presentation, we will briefly review General Electric's InSb Charge Injection Device technology. Emphasis will be placed on device performance as a function of material parameters. A new InSb materials technology utilizing liquid phase epitaxy will be described. This epitaxial growth technology improves InSb material parameters and increases minority carrier lifetimes by more than two orders of magnitude to near the Auger limit. Comparisons will be made between available bulk material parameters and that of the epitaxial material.

Mercury cadmium telluride (Hg1-x Cdx Te) is an important material for infrared detector applications due to tde variable bandgap obtained through simply varying the mercury/cadmium ratio. Thus IR sensing systems with various wavelength requirements, typically from 2 to 12 μm, can potentially all be supplied by one materials technology. Bulk crystal growth technology was originally pursued for these applications. However, large, high quality crystals are difficult to grow because of the high melting point of HgCdTe and the resulting high Hg vapor pressure. Liquid phase epitaxial (LPE) growth techniques can lower the growth temperature through the use of a solvent, and allow the deposition of thin films on large foreign substrates that are grown without any Hg.

InSb1−x Bix (0.01 < × < 0.14) and InAsSbBi quaternary alloys are potentially attractive materials for the development of semiconductor infrared detectors covering the 8–14 μm range [1,2,3].

We report for the first time, MOCVD growth of InSo1−x Bix (0.01 < × < 0.14) and InAs1−x−y Sbx Biy with 0.5 < × < 0.7 and 0.01 < y < 0.04 on both GaAs and InSb substrates using AsH3, TMSb, TEI and TMBi. Electrical measurements of the undoped InSo0.99 Bi0.01 shows a background carrier concentration of approximately 1016/cm3 and a room temperature mobility of 20,215 cm2/V.sec. To-date, these are the best reported electrical measurements for this ternary alloy.

The formation of a secondary Bi phase and single crystal growth of metallic bismuth-antimony at the surface of InSo1−x Bix which results in deterioration of morphology with increasing values of x is also investigated. A wide range of analytic techniques, including SEM, EDX, electron microprobe and AES have been employed in our surface analysis.

CD1−xZnxTe alloys of various composition have been grown by the Molecular Beam Epitaxy Technique and characterized by Transmission Electron Microscopy. C(V) measurements and photoluminescence spectroscopy techniques. The quality of the thick layers is comparable to that of bulk material. Thin strained layers have also been grown whose interfaces are structurally good. The recombination within a CdTe well confined between Cd1−xZnxTe barriers is dominated by intrinsic processes.

Experiments have been performed to assess the feasibility of using ionbeam sputter deposition for the growth of CdTe, HgTe and HgCdTe films. Some simple cryogenically cooled dual-target configurations have been employed in an investigation of epitaxial growth on CdTe substrates. Good-quality epitaxy was achieved for CdTe at temperatures down to 140°C, and for HgTe and HgCdTe at temperatures extending to below 50° C.Based upon compositional and phase analyses, and upon IR absorption measurements, we conclude that, using an excess Hg flux, stoichiometric transfer of the HgCdTe target composition to the substrate is approximately obtained. However, some departure from stoichiometry is produced at higher substrate temperatures (> 150”C) due to thermal re-evaporation of Hg, and under high sputtered Hg fluxes due to selective re-sputtering of HgTe. The good structural quality and excellent compositional uniformity of the films indicate that ion-beam sputter deposition may be suitable for low-temperature processing of IR detector structures.

Cadmium telluride layers were grown on InSb substrates by organometallic vapor phase epitaxy and examined using secondary ion mass spectrometry (SIMS), photoluminescence (Pb) and double crystal x-ray diffraction (DCD). The substrate temperature and the nature of the surface prior to growth are shown to be the most important parameters which influence the quality of CdTe layers. Growth on diethyltelluride (DETe) stabilized InSb substrates resulted in CdTe growth with a misorientation of about 4 minutes of arc with respect to the substrates. On the other hand, the grown layers followed the orientation of the substrates when a dimethylcadmium (DMCd) stabilized InSb was used. Growth at 350°C resulted in the smallest x-ray rocking curve (DCRC) full width at half maximum (FWHM) of about 20 arc seconds.

GaSb, InSb and InAs epitaxial layers with mirror surface were grown on GaSb, GaAs, InP, Si and sapphire substrates at relatively low temperatures by plasma-assisted epitaxy (PAE) in hydrogen plasma. Carrier concentrations and Hall mobilities of undoped PAE layers at room temperature are p=6×O16 cm−3; μp=750cm2/Vs, n=1×1016cm−3; μn=39,000cm2/Vs and n=7×1017 cm−3; μn=21,000cm2/Vs for GaSb on GaAs, InSb on GaAs and InAs on InP, respectively. As the first application of PAE layers to optoelectronic devices, p-GaSb/n-GaAs heterojunction photodiodes have been demonstrated to result in remarkable reduction of dark current with photoresponse in the wavelength region between 0.85 and 1.7μm for the light incident from GaAs.