STUDY OF ELECTRON TRAPS IN SEMIINSULATING GALLIUM-ARSENIDE BUFFER LAYERS FOR THE SUPPRESSION OF BACKGATING BY THE ZERO-BIAS THERMALLY STIMULATED CURRENT TECHNIQUE

Electron traps in undoped-GaAs epitaxial layers grown at low temperatures ( <300-degrees-C) by molecular beam epitaxy were studied by the zero-bias thermally stimulated current technique. Four traps T1-4 were detected in as-grown samples. It was also found that all the traps detected can be annealed out except the T1 trap. However, the buffer layer, with or without annealing, was found to be an effective remedy for backgating in high electron mobility transistors, indicating that the T1 trap may have a much more significant role than the three shallower traps in the suppression of backgating. The T1 trap is believed to be the EL3 electron trap which is related to oxygen contamination.