THE MINORITY-CARRIER LIFETIME IN DOPED AND UNDOPED P-TYPE HG0.78CD0.22TE LIQUID-PHASE EPITAXY FILMS

This paper will describe: (1) the first comparative study of recombina tion mechanisms between doped and undoped p-type Hg1-xCdxTe liquid pha se epitaxy films with an x value of about 0.22, and (2) the first dete rmination of tau(A7)(i)/tau(A1)(i) ratio by lifetime's dependence on b oth carrier concentration and temperature. The doped films were either copper- or gold-doped with the carrier concentration ranging from 2 x 10(15) to 1.5 x 10(17) cm(-3), and the lifetime varied from 2 mu s to 8 ns. The undoped (Hg-vacancy) films had a carrier concentration rang e between 3 x 10(15),and 8 x 10(16) cm(-3), and the lifetime changed f rom 150 to 3 ns. It was found that for the same carrier concentration, the doped films had lifetimes several times longer than those of the undoped films, limited mostly by Auger 7 and radiative recombination p rocesses. The ineffectiveness of Shockley-Read-Hall (SRH) recombinatio n process in the doped films was also demonstrated in lifetime vs temp erature curves. The important ratio of intrinsic Auger 7 lifetime to i ntrinsic Auger 1 lifetime, tau(A7)(i)/tau(A1)(i), was determined to be about 20 from fitting both, concentration and temperature curves. The reduction of minority carrier lifetime in undoped films can be explai ned by an effective SRH recombination center associated with the Hg va cancy. Indeed, a donor-like SRH recombination center located at midgap (E(v)+60 meV) with a capture cross section for minority carriers much larger than that for majority carriers was deduced from fitting lifet ime vs temperature curves of undoped films.