Transient and steady-state lifetime measurements on epitaxially grown Cd_xHg_1-xTe

Abstract

There is still considerable controversy in the field of recombination mechanisms in CdxHg1-xTe (CMT), particularly with regard to those operating in p-type material. It is vital to understand this behaviour if improvements in device performance are to be made. This paper reports on lifetime measurements made on both liquid phase epitaxial (LPE) and metal-organic vapour phase epitaxial layers. Factors studied include the influence of surfaces, substrate/layer interfaces and the dependence of lifetime on carrier concentration and temperature. The effect of different post-growth annealing schedules has also been considered and comparisons made between MOVPE material doped with acceptor impurities and that controlled by metal vacancies. As transient photoconductive decay results did not produce the trends expected from device results at 192 K, measurements have been made under steady-state conditions for representative samples. These steady-state lifetimes are the first reported in MOVPE material and are augmented by estimates of capture rates and densities of traps.