DOMINANT TRAPS IN LIQUID-PHASE EPITAXIAL GAAS STUDIED BY CONTROLLED DOPING WITH INDIUM AND ANTIMONY

Photocapacitance measurements in the photon energy range of 0.64 to 1. 27 eV are done on GaAs layers grown by liquid phase epitaxy (LPE) and doped with varying amounts of indium (In) and antimony (Sb). Two hole traps with optical ionization energies of 0.65 and 0.79 eV are reveale d in the material which are assumed to be two levels associated with t he hole trap in reported in the literature. In addition, the hole trap A, usually found in LPE GaAs is also detected here by optical deep le vel transient spectroscopy (ODLTS) technique. The results of trap dens ity measurements, as functions of isoelectronic doping concentration, indicate that V(Ga) is an active constituent of the hole traps in LPE GaAs. The concentration of the 0.79 eV trap is found to be reduced in the material with high concentration of Sb. The analysis of photocapit ance data using the existing theoretical models indicates the presence of an electron trap with activation energy of 0.75 eV in the heavily Sb-doped material. This trap may be identified with the second charge state of the Sb(Ga) electron trap, obtained previously in bulk and met alorganic vapor phase epitaxial GaAs doped with Sb. The sharp reductio n of the 0.79 eV hole trap density in Sb-doped materials is explained by assuming the complex Ga(As)V(Ga)- as its source.