High-resolution photoinduced transient spectroscopy as a new tool for quality assessment of semi-insulating GaAs

High-resolution photoinduced transient spectroscopy (HRPITS) has been applied to study the electronic properties of grown-in point defects in semi-insulating (SI) GaAs bulk crystals grown by liquid encapsulated Czochralski (LEC) and vertical gradient freeze (VGF) methods. The novel method, which represents the significant improvement of the earlier PITS technique, relies on the extraction of trap parameters from the digitally recorded photocurrent transients by means of the correlation procedure. The influence of the crystallisation conditions on the defect structure of high resistivity GaAs is compared. In the VGF material the concentrations of traps P6 (0.05 eV), P7 (0.08 eV), P12 (0.18 eV), EL14 (0.22 eV) and EL3 (0.58 eV), tentatively identified as VAs−/0, GaAs0/−, BAs−/−−, VGa–VAs and Oi–VAs, respectively, are found to be much lower than in the LEC material.