DEEP LEVELS IN ZNSE EPITAXIAL LAYERS EXAMINED BY PIEZOELECTRIC PHOTOACOUSTIC-SPECTROSCOPY

Piezoelectric photoacoustic (PPA) measurements of nondoped ZnSe epitax ial layers grown by molecular beam epitaxy (MBE) are carried out at ro om and liquid nitrogen temperatures. Distinct peaks due to the band-ga ps of ZnSe and the substrate GaAs are clearly observed. Five PPA peaks are observed in the nondoped ZnSe thin films with VI/II ratio of 12 a t liquid nitrogen temperature for the first time. This indicates that five types of intrinsic defects exist in ZnSe epitaxial layers. The ob tained energies of these defects are 1.20 +/- 0.01, 0.97 +/- 0.03, 0.6 5 +/- 0.03 and 0.06 +/- 0.01 eV, respectively. (C) 1998 Elsevier Scien ce B.V. All rights reserved.