HETEROEPITAXY OF HGCDTE (211)B ON GE SUBSTRATES BY MOLECULAR-BEAM EPITAXY FOR INFRARED DETECTORS

Epitaxial growth of (211)B CdTe/HgCdTe has been achieved on two inch g ermanium (Ge) by molecular beam epitaxy (MBE). Germanium was chosen as an alternative substrate to circumvent the weaknesses of CdZnTe wafer s. The ease of surface preparation makes G;e an attractive candidate a mong many other alternative substrates, Best MBE CdTe growth results w ere obtained on (211) Ge surfaces which were exposed to arsenic and zi nc fluxes prior to the MBE growth. This surface preparation enabled Cd Te growth with B-face crystallographic polarity necessary for the HgCd Te growth. This process was reproducible, and produced a smooth and mi rror-like surface morphology. The best value of the {422} x-ray double diffraction full width at half maximum measured fr om the HgCdTe laye r was 68 arc-s. We present the 486 point maps of FWHM statistical valu es obtained from CdTe/Ge and HgCdTe/CdTe/Ge. High resolution microscop y electron transmission and secondary ion mass spectroscopy characteri zation results are also presented in this paper. High-performance midd le wavelength infrared HgCdTe 32-element photodiode linear arrays, usi ng the standard LETI/LIR planar n-on-p ion implanted technology, were fabricated on CdTe/Ge substrates. At 78K, photodiodes exhibited very h igh R(0)A figure of merit higher than 10(6) Ohm cm(-2) for a cutoff wa velength of 4.8 mu m Excess low frequency noise was not observed below 150K.