DETECTION OF SURFACE-STATES IN GAAS AND INP BY THERMALLY STIMULATED EXOELECTRON EMISSION-SPECTROSCOPY

The energy distribution and relative densities of electronically activ e surface defects have been studied using thermally stimulated exoelec tron emission (TSEE) spectroscopy. This novel and relatively simple te chnique has high sensitivity for detecting the surface states which ar e difficult to assess by other techniques. Here this technique is succ essfully used for detecting the pinned positions of the Fermi level in n-GaAs and n-InP which are, respectively, 0.91 and 0.43 eV below the conduction bands corresponding to 2E(g)/3 and E-g/3 as expected. Antis ite and oxygen related defects in these semiconductors are also identi fied at the surface. The relative TSEE peak intensities correlate very closely to the reported surface recombination velocities for these ma terials which are two to three orders of magnitude higher for GaAs. Th e effect of chromium on the surface states in these semiconductors, st udied using semi-insulating GaAs, showed partial passivation of the su rface defects in semi-insulating GaAs resulting in unpinning of the Fe rmi levels. Fe doped InP did not, however, show any sign of dopant ind uced deep levels. (C) 1997 American Institute of Physics.