Annealing behavior of deep-level defects in 1 MeV electron irradiated GaAs

Abstract

Isochronal annealing behavior of deep-level defects in 1 MeV electron irradiated vapor phase epitaxy GaAs was studied through deep level transient spectroscopy measurements. As the annealing temperature was increased, the activation energy of the EL2-A trap remained at Ec−0.823 eV, whereas the EL2-B trap (Ec−0.843 eV) transformed into a new trap, ELN-1 (Ec−0.870 eV), and finally into another new trap, ELN-2 (Ec−0.891 eV) before returning to the single EL2-A level at a 270 °C annealing temperature. The EL6 trap (Ec−0.335 eV) varied similarly, transforming into Ec−0.357 eV (P1) before staying constant at Ec−0.396 eV (ELN-3) after a 270 °C annealing temperature. The capture cross sections of EL2-B and EL6 increased by an order of magnitude during the annealing. These results suggest that the EL2-B trap which was split from the EL2 center by the 1 MeV electrons could be related to EL6. Traps E1 and E2 remain at Ec−0.032 eV and Ec−0.129 eV, respectively, throughout the annealing, before annihilation at a 290 °C annealing temperature. This result indicates that the atomic structures of E1 and E2 defects could be related. The EL3 (Ec−0.420 eV) is transformed into a new trap, ELN-4 (Ec−0.456 eV), and then into Ec−0.50 eV (P2) during annealing. The free carrier concentration of the irradiated sample increases rapidly with annealing temperature and returns back to the starting free carrier concentration due to the rapid annealing rates of the electron induced defects.