Deep levels in ZnSe epitaxial layers examined by piezoelectric photoacoustic spectroscopy

Piezoelectric photoacoustic (PPA) measurements of nondoped ZnSe epitaxial layers grown by molecular beam epitaxy (MBE) are carried out at room and liquid nitrogen temperatures. Distinct peaks due to the band-gaps 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 at liquid nitrogen temperature for the first time. This indicates that five types of intrinsic defects exist in ZnSe epitaxial layers. The obtained energies of these defects are 1.20 +/- 0.01, 0.97 +/- 0.03, 0.65 +/- 0.03 and 0.06 +/- 0.01 eV, respectively. (C) 1998 Elsevier Science B.V. All rights reserved.