EL2 DEEP-LEVEL TRANSIENT STUDY IN SEMIINSULATING GAAS USING POSITRON-LIFETIME SPECTROSCOPY

Positron lifetime measurements performed on Au/GaAs samples at room te mperature with an applied square-wave ac bias show a frequency depende nt interface related lifetime intensity that peaks around 0.4 Hz. The observation is explained by the ionization of the deep-donor level EL2 to EL2(+) in the GaAs region adjacent to the Au/GaAs interface, causi ng a transient electric field to be experienced by positrons drifting towards the interface. Without resorting to temperature scanning or an y Arrhenius plot the EL2 donor level is found to be located 0.80+/-0.0 1+/-0.05 eV below the conduction-band minimum, where the first error e stimate is statistical and the second systematic. The result suggests positron annihilation may, in some instances, act as an alternative to capacitance transient spectroscopies in characterizing deep levels in both semiconductors and semi-insulators.