OPTICAL PROPERTIES OF N-TYPE GAAS .2. FORMATION OF EFFICIENT HOLE TRAPS DURING ANNEALING IN TE-DOPED GAAS

The photoluminescence intensity of the near gap emission from Te-doped GaAs crystals decreases greatly after annealing at temperatures ranging from 600°to 1000°C while at the same time the intensity increases in the 1.22-eV band. The decrease in the near gap emission is less for samples annealed at higher temperatures for durations equal to the equilibrium annealing times. These results are shown here to be due to the creation of efficient hole traps whose concentration is proportional to the decrease in concentration of Te donors during annealing. The formation kinetics of these traps follows the form Nx(t)=Nx(∞){1-exp[-(t/R)0.44]} where Nx(t) and Nx(∞) are, respectively, the trap densities at annealing time t and at equilibrium, and R is the time constant for the formation process. This process is characterized by an activation energy of about 0.8 eV in the temperature range studied. The above facts when coupled with the observed increase of the 1.22-eV band emission lead to an identification of the traps as Te donor-Ga vacancy complexes which are identical to those responsible for the 1.22-eV band. © 1969 The American Institute of Physics.