Quantitative Detection of Oxygen Contamination Related Traps in Gallium Arsenide Epitaxial Layer Grown by Molecular Beam Epitaxy at Low Temperature

Using a new technique, zero quiescent bias voltage transient current spectroscopy (ZBTCS), a semi-insulating GaAs epitaxial layer grown by MBE at 230°C is found to have a continuum of states with some discrete traps. The dominant discrete electron trap has an activation energy of 0.55 eV and a concentration of the order of 10 17 cm -3 . This trap is believed to be the EL3 electron trap related to oxygen contamination. Quantitative secondary ion mass spectroscopy (SIMS) measurements confirms that GaAs epitaxial layers tend to be contaminated by oxygen when the growth temperature is low. The role of an ammonium sulphide surface treatment on the measured trap concentration is also discussed.