Stretched-exponential photoionization of the metastable defects in gallium doped Cd0.99Mn0.01Te: Statistical origins of the short-time power-law in response data

The subject of the present study is the low temperature nonexponential transients of photoconductivity build-up in gallium doped Cd0.99Mn0.01Te semiconducting mixed crystals possessing metastable defects, so called DX centers. The phototransients were analyzed in terms of two approaches. The first one was the two-exponential fitting that is usually applied to explain the persistent photoeffect build-up in materials with DX centers. The second, implemented in the above-mentioned semiconductors, was the stochastic model of relaxation leading to the stretched-exponential result. The latter fitting was found to be more appropriate for it justifies the short-time power-law exhibited by the phototransient response. According to the stochastic approach this behavior results from a heavy-tailed distribution of photoionized DX centers. The distribution can have its origin in different local arrangements.