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 recombination mechanisms between doped and undoped p-type Hg_1-xCd_xTe liquid phase epitaxy films with an x value of about 0.22, and (2) the first determination of τ_A7 ⁱ/τ_A1 ⁱ ratio by lifetime’s dependence on both carrier concentration and temperature. The doped films were either copper- or gold-doped with the carrier concentration ranging from 2 x 10¹⁵ to 1.5 x 10¹⁷ cm^-3, and the lifetime varied from 2 μs to 8 ns. The undoped (Hg-vacancy) films had a carrier concentration range between 3 x 10¹⁵ and 8 x 10¹⁶ cm^-3, and the lifetime changed from 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 processes. The ineffectiveness of Shockley-Read-Hall (SRH) recombination process in the doped films was also demonstrated in lifetime vs temperature curves. The important ratio of intrinsic Auger 7 lifetime to intrinsic Auger 1 lifetime, τ_A7 ⁱ/τ_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 explained by an effective SRH recombination center associated with the Hg vacancy. 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 lifetime vs temperature curves of undoped films.