CONTACT-RELATED DEEP STATES IN THE AL-GAINP/GAAS INTERFACE

Deep levels have been measured in a molecular beam epitaxy grown Ga0.51In0.49P/GaAs heterostructure by double correlation deep level transient spectroscopy. Gold (Au) and aluminum (Al) metals were used for a Schottky contact. A contact-related hole trap with an activation energy of 0.50-0.75 eV was observed at the Al/GInP interface, but not at the Au/GaInP interface. To our knowledge, this contact-related trap has not been reported before. We attribute this trap to oxygen contamination, or a vacancy-related defect, V-In or V-Ga. A new electron trap at 0.28 eV was also observed in both Au- and Al-Schottky diodes. It depth profile showed that it is a bulk trap in a GaInP epilayer. The temperature dependent current-voltage characteristics show a large interface recombination current at the GaInP surface due to the Al contact. The energy distribution of the interface state density showed a maximum at E(V)+0.85 eV within the band gap. Concentration of the interface trap and the magnitude of recombination current are both reduced by a rapid thermal annealing at/or above 450 degrees C after aluminum deposition. The Al Schottky barrier height also increased after a 450 degrees C annealing.