High operating temperature (HOT) detector concepts using midwave infrared (MWIR) (x ϳ 0.3) p-type HgCdTe operating at temperatures within the thermoelectric cooler range are of significant interest at the present time. However, it is apparent that much work remains to be done in the areas of material, diode passivation, and diode formation technologies before the "holy grail" of photon detection at room temperature for all infrared wavelengths is achieved. Over the years, at DRS, we have developed a technology base for both n-and p-type HgCdTe materials parameters that are relevant to photodiode design and fabrication. This paper will discuss data that we have taken recently on minority carrier lifetime in MWIR and long wave infrared (LWIR) HgCdTe, particularly p type, and how it compares to current theories of Auger 7, radiative, and Shockley-Read recombination in this material. Extrinsic group IB (Cu, Au) and group V (arsenic) p-type dopants were used, together with group III (In) for n-type. The impact of the data on future HOT detector work is discussed.

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Many methods for the preparation of (Hg,Cd)Te alloys rely on a low temperature processing step to convert the as-grown p-type material to n-type, or to otherwise adjust the concentration of native acceptors. During this anneal, tellurium precipitates in the material are annihilated by in-diffusing mercury, resulting in a substantial multiplication of dislocations. For substantially long anneals (>1 day at 270 °C) the depth of the p–n junction is found to vary as the square root of the anneal time and inversely as the square root of the excess tellurium concentration. Rapidly diffusing impurities such as silver are gettered out of the skin and into the remaining vacancy-rich core. The kinetics of these processes are analyzed for self-diffusion on the metal sublattice involving only vacancies, only interstitials, and for a mixed vacancy–interstitial model. Comparison with experimental data shows best agreement with the mixed interstitial–vacancy model.

A new fastresponse Hg vapor source for HgCdTe molecularbeam epitaxy growthThe surface kinetics that govern molecular-beam epitaxial (MBE) growth of HgCdTe films places strict boundaries on the optimal deposition conditions to be selected. This paper will examine the limits imposed by the surface kinetics on the Hg flux, substrate orientation, and substrate temperature to be chosen for MBE HgCdTe film growth. The range ofHg flux available to grow single-crystalline HgCdTe (as determined by reflection high-energy electron diffraction) will be seen to vary significantly with the (112)Te, (l12)Cd, and (001) growth orientations. The HgCdTe(l12)Te films are deposited with a high Hg condensation coefficient at 200°C (0.04-0.10), have an excellent surface morphology, and avoid the cellular twins that are found in HgCdTe( 111 )Te layers. However, each of the three orientations result in faceted growth at substrate temperatures near 200°C; at this substrate temperature, HgTe begins to desorb from the growth surface which leads to a preferential exposure of the lower energy (111) planes. Due to the variation in the HgTe growth rate with facet orientation, the HgCdTe films grown near 200°C are found to have significant lateral compositional inhomogeneities.

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