Millisecond phosphorescence of free electrons in pure GaAs

Abstract

A very long decay of transient free-to-bound photoluminescence (PL) in pure GaAs at low temperatures has been experimentally found. It is shown that, in undoped or dilutely doped GaAs, the decay of band-to-acceptor PL after a transient excitation follows an essentially nonexponential dependence approximated by a power law with the exponent as low as 0.3, and is observed for as long as 2.5 ms. The long decays of free-electron PL point to the domination of repeated trappings and subsequent releases of free electrons by some shallow traps, which are suggested to be the shallow donors.