MEASUREMENT OF MINORITY-CARRIER LIFETIME IN N-TYPE MBE HGCDTE AND ITSDEPENDENCE ON ANNEALING

Results are presented for minority carrier lifetime in n-type molecula r beam epitaxy Hg1-xCdxTe with x ranging from 0.2 to 0.6. It was found that the lifetime was unintentionally degraded by post-growth anneali ng under Hg Saturated conditions in a H, atmosphere that was both time and temperature dependent. This effect was minimal or non-existent fo r x similar to-0.2 material, but very strong for x greater than or equ al to 0.3. Hydrogen was identified as responsible for this degradation . Identical annealing in a He atmosphere avoids this degradation and r esults in near-theoretical lifetime values for carrier concentrations as low 1 x 10(15) cm(-3) in greater than or equal to 0.3 material. Mod eling was carried out, for x similar to 0.2 and x similar to 0.4 mater ial that shows the extent to which lifetime is reduced by Shockley-Rea l-Hall recombination for carrier concentrations below 1 x 10(15) cm(-3 ), as well as for layers annealed in H-2. It appears that annealing in H, results in a deep recombination center in wider bandgap HgCdTe tha t lowers the lifetime without affecting the majority carrier concentra tion and mobility.