Deep hole traps in Be-doped Al0.5Ga0.5As layers grown by molecular beam epitaxy

Deep hole traps in p-type Al0.5Ga0.5As grown by molecular beam epitaxy have been studied by the deep-level transient-spectroscopy method applied to samples with a Schottky diode configuration. Five hole traps, labeled as H0 to H4, were found. For traps H1, H3, and H4 the activation energies for emission were E-T1 = 0.14 eV, E-T3 = 0.40 eV, and E-T4 = 0.46 eV, respectively. Hole emission from trap H2 was dependent on the external electric field. The emission rate obeyed the Poole-Frenkel relation. When extrapolated to zero electric field, the thermal activation energy for hole emission was E-T2,E-0 = 0.37 eV. Capture cross sections for traps H1 and H4 were thermally activated with energy barriers E-B1 = 0.04 eV and E-B4=0.18 eV, respectively. (C) 1999 American Institute of Physics. [S0021-8979(99)04115-8].