Study of grown-in deep-level defects vs growth parameters in GaAs grown by VPE technique
Studies of the grown-in deep level defects vs substrate orientation and gas phase stoichiometry in the VPE GaAs grown by a novel Ga/AsCl3/H2 reactor has been made, using DLTS and C-V methods. Density of electron traps vs Ga/As ratio (i.e., 2/1, 3/1, 4/1, 5/1, and 6/1) was determined for epilayers grown on (100), (211A), and (211B) oriented semi-insulating Cr-doped GaAs substrates. Two electron traps with energies of Ec-0.71 eV (i.e., EB-4) and Ec-0.83 eV (i.e., EL-2) were observed in the samples studied. Results showed that density of both electron traps depends strongly on the Ga/As ratio for the (211A) oriented samples, and less strongly for the (100) oriented samples. In both cases, however, the defect density was found to decrease with increasing Ga/As ratio. This result was consistent with the published data in GaAs grown by the VPE, MOCVD, and LEC techniques. Combined thermal and recombination enhanced annealing study on these VPE GaAs specimens showed a significant reduction in the density of the EB4 level and a little reduction in the density of the EL2 level. This