Oxygen in GaAs and its relation to the EL3 defect investigated by TSC and PICTS

¹ Institut für Experimentelle Physik, TU Bergakademie Freiberg, Silbermannstr. 1, Freiberg, 09599, Germany
² Freiberger Compound Materials GmbH, Am Junger Löwe Schacht 5, Freiberg, 09599, Germany
³ Institut für Kristallzüchtung, Max-Born-Str. 2, Berlin, 12489, Germany

Corresponding author: Anke.Wohlrab@physik.tu-freiberg.de

Received: 11 September 2003
Accepted: 19 March 2004
Published online: 15 July 2004

Abstract

Thermally stimulated current (TSC) and photo induced current transient spectroscopy (PICTS) were used to investigate deep traps in oxygen-rich medium resistivity GaAs. We observed an abnormal behaviour of the TSC signal at a temperature of about 200 K, where the TSC current is lower than the dark current. This results in a negative peak occurring in the temperature range where the signal of the well known EL3 defect in undoped semi-insulating GaAs is present. For verification, comparative PICTS-measurements were performed, which exhibit the same negative peak at similar temperatures. The activation energy for this negative peak was determined to be ~ 0.6 eV (TSC). This is in good agreement with published values for the EL3 ranging from 0.56 to 0.68 eV. Furthermore, we illustrate that the depth of the peak increases with increasing oxygen content. Our results support the assumption, that oxygen on an arsenic site – the so called off centre oxygen oc-O_As – should be the origin of the EL3.