A study of deep levels in vanadium-doped GaAs grown by OMVPE

Abstract

Vanadium(V)-doped GaAs layers grown by metal organic vapour phase epitaxy using vanadium tetrachloride as a doping source were characterized by deep level transient spectroscopy. The only deep level detected in undoped GaAs is EL2. After V doping, the EL2 defect was not detected. This observation is explained by a reaction involving V and the EL2 arsenic antisite. V doping creates an electron trap (E1) at 0.14 eV below the conduction band, associated with the transition V3+/V2+, and a broad band (E2) of electron traps. The E1 concentration increases with increasing V doping to reach a maximum value of 1016 cm−3 for a total V concentration of about 1018 cm−3. The E2 band is characterized by a defect distribution similar to the so-called U band. We propose that it is associated with intrinsic defects introduced by the growth conditions.