Slow decay of photoconductivity caused by tin-related DX centers in AlGaAs

Capacitance decay after termination of light was measured on AlxGa1-xAs/GaA s heterostructures with p-n junctions. It has been shown that the decay can be well expressed by two curves of stretched exponential forms; exp[-(t/ta u)(beta)]. The temperature dependence of the characteristic time tau of eac h of the two curves was determined in the range from 15 K to 60 K. The depe ndence follows the theoretical relation for electron capture dominated by t unneling via multiphonon emission. The estimated capture parameters show a strong electron-phonon coupling of two DX centers. Possible relation of the se centers to tin is discussed.