Nature of the bulk defects in GaAs through high-temperature quenching studies

Abstract

Deep-level transient spectroscopy has been applied to n-type horizontal gradient freeze grown GaAs that has been subjected to thermal stressing (quenching) and varying degrees of arsenic outdiffusion during rapid thermal annealing. The concentrations and activation energies of the various deep donor levels have been monitored. As a result of the external excitations in the lattice due to the thermal stress (quenching), dramatic effects occur in the defect level structure that could be of importance to device technology. It is found that the native EL6 group of defects is nearly absent in rapid thermally annealed material, while the levels EL5 and EL8 appear with EL3 becoming a dominant level that could act as a recombination center. With the lengthening of annealing time and significant As outdiffusion, there is a general reduction of the EL2, EL3, and EL5 defect concentrations together with a complete removal of EL8. Moreover, the EL2 activation energy may be varied from 0.827 to 0.922 eV by controlling the level of As out-diffusion. These observations are discussed in terms of the As Ga-As i model of the EL2 defect and the V As-V Ga divacancy model for the EL6 group of defects. The EL3, EL5, EL8, and EL15 defect levels seen in samples subjected to rapid thermally quenching are attributed to the breakup of V As-As i Frenkel pair defects known to be present in the as-grown material.