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.

The results of arsenic incorporation in HgCdTe layers grown by molecular beam epitaxy (MBE) are reported. Obtained results indicate that arsenic was successfully incorporated as acceptors in MBE-HgCdTe layers after a low temperature anneal. Secondary ion mass spectrometry and Hall effect measurements confirm that arsenic is incorporated with an activation yield of up to 100%. This work confirms that arsenic can be used as an effective dopant of MBE-HgCdTe after a low temperature annealing under Hg-saturated conditions.

Carrier recombination lifetime measurements and analyses based on Shockley-Read-Hall, radiative, and Auger recombination mechanisms were utilized to characterize the material quality of HgCdTe grown by molecular beam epitaxy. The Auger recombination mechanism employed in this analysis is in the theoretical framework according to Beattie and Landsberg ͓Proc. R. Soc. London, Ser. A 249, 16 ͑1959͔͒, which we independently re-evaluated using the electronic band structures computed with a 14-band k · p methodology and direct evaluations of the transition rates. The Levenberg-Marquette method was used to fit the temperature-dependent carrier recombination lifetimes as measured by the photoconductive decay technique. Based on the above methods, carrier recombination lifetime measurements were developed as a routine characterization technique.

Void defects were demonstrated to form away from the substrate-epifilm interface during the molecular beam epitaxial growth of mercury cadmium telluride on cadmium zinc telluride substrates. These were smaller in size compared to voids which nucleated at the substrate-epifilm interface, which were also observed. Once nucleated, voids usually replicated all the way to the surface even if the flux ratios were modified to prevent additional nucleation of voids. Occasionally, void defects which close before reaching the top surface without leaving any perturbations on the surface, have also been observed. The voids which form away from the substrate-epi interface, nucleate on defects, frequently hillocks, introduced into the film already grown, leading to formation of defect complexes. These voids can be smaller than 1 µm and appear almost indistinguishable from unaccompanied simple voids. However, these void-hillock complexes displayed a nest of dislocations decorating these defects, which become apparent upon dislocation etching, whereas unaccompanied simple voids did not. The nests could extend as much as 25 µm from the individual void-hillock complex. The density of dislocations within the nest exceeded 5 x 10 6 cm -2 , whereas the dislocation density outside of the nest could decrease to < 2 x 10 5 cm -2 .

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