The sulfur-related trap in GaAs1−xPx

Abstract

A systematic study has been made of the deep level introduced into GaAs_1−xP_x alloy material by S doping. Conclusive documentation of the linear relationship between S concentration and the deep‐level trap concentration is presented for x?0.4. The dynamic properties of this trap measured at x=0.38 show a temperature activation energy for emission and electron capture of 0.35 and 0.15±0.03 eV, respectively. It exhibits a very large hole‐capture cross section at a site occupied by an electron. A very sharp drop in the ability to populate the trap below x=0.35 is consistent with the trap being energetically tied to the X band minimum and having a depth of 0.17 eV below this band minimum. The dependence of the thermal‐emission activation energy on alloy composition is ascribed to the necessity to capture electrons from the indirect minima below x?0.4. Photoionization experiments indicate that a much greater photoenergy than the thermal energy is required to ionize an electron trapped at this site (1.1 compared to 0.17 eV). Electron capture followed by a large lattice relaxation is consistent with the data and the phenomenon of persistent photoconductivity at low temperature associated with the S center. The S center in GaAs_1−xP_x provides an efficient nonradiative recombination path for minority carriers.