Isothermal capacitance transient spectroscopy (ICTS) study for midgap levels in Hb-GaAs by rapid thermal annealing

We studied the midgap levels by using isothermal capacitance transient spectroscopy (ICTS) in Hb-GaAs which had been processed by rapid thermal annealing (RTA). As the annealing time at 850 °C increased, the EL2 trap (E _c–0.81 eV) was transformed to the EX2 trap (E _c–0.73 eV) and eventually to the EX1 trap (E _c–0.87 eV). The diffusivity of the EL2 trap obtained from the experimental result of the heat treatment was about 1.02·10^–8cm²/s at 850 °C. This result indicate that the EL2 trap contains an interstitial arsenic atom. The result of the transformation to the EX1 and EX2 traps suggests that, when the EL2 trap is V_AsAS_iV_GaAs_Ga, the EX2 trap may be V_AsV_GaAs_Ga, which As_i is diffused out during a thermal annealing.