IDENTIFICATION OF DEEP DEFECTS IN HIGH-RESISTIVITY UNDOPED LEC-GAAS IRRADIATED WITH PROTONS

Deep levels related to defects in high-resistivity undoped LEC-GaAs, g enerated during the growth and by low-fluence proton irradiation (2.6 x 10(10)-1.3 x 10(11) cm(-2)) are investigated by means of photo-induc ed current transient spectroscopy (PICTS). In order to compare effects from defects in the volume and defects in the surface of the material on PICTS observations, sandwich Schottky diodes and planar samples wi th two ohmic contacts on the front face were studied. Five main traps were observed. In addition to apparent activation energies, it is show n that the nature of carrier traps can also be identified. Irradiation with protons results in the creation of a new electron trap at nearly 0.72 eV below the conduction band. It is also shown that significant modifications in PICTS results may occur when changing the wavelength of the exciting light. In order to check the reliability of the deduct ions made from PICTS related to the nature of the observed traps, deep level transient spectroscopy (DLTS) measurements were performed under a permanent illumination of the sample. A general comparison and disc ussion are based on the results obtained from these different techniqu es.