Effect of thermal annealing on band edge absorption spectrum

Abstract

We report the effects of annealing temperature on the near-band-gap transmittance, the absorption coefficient. and the evolution of shallow-level defects of arsenic-ion-implanted GaAs (hereafter referred to as GaAs:As+) using Fourier-transform infrared spectroscopy. The maximum above-band-gap transmittance and absorption coefficient are determined to be 0.4 and 6 x 10(3) cm(-1), respectively. An anomalous absorption peak at the photon energy of 1.37-1.4eV for the GaAs:As+ samples annealed at lower than 500 degreesC is observed. By either fitting the absorption curve, the band-gap energy of rapid-thermal-annealed GaAs:As+ is evaluated. which blue shifts from 1.36 eV to 1.41 eV as the annealing temperature increases from 300 degreesC to 800 degreesC. The slightly rising absorption spectra at the near-band-gap region suggest the existence of defects and scattering centers. The activation energies and formatting mechanisms of the dense defects in the Rapid-thermal-annealed GaAs:As+ samples were identified, By characterizing the differential absorption spectra, the eVolution of some defect-related absorption bands during the high-temperature annealing process were observed and the correlated structural phenomena were explained.