Compensation And Persistent Photocapacitance In Homoepitaxial Sn-Doped Beta-Ga2o3

The electrical properties of epitaxial beta-Ga2O3 doped with Sn (10(16)-9 x 10(18) cm(-3)) and grown by metalorganic chemical vapor deposition on semi-insulating beta-Ga2O3 substrates are reported. Shallow donors attributable to Sn were observed only in a narrow region near the film/substrate interface and with a much lower concentration than the total Sn density. For heavily Sn doped films (Sn concentration, 9 x 10(18) cm(-3)), the electrical properties in the top portion of the layer were determined by deep centers with a level at E-c-0.21 eV not described previously. In more lightly doped layers, the E-c-0.21 eV centers and deeper traps at E-c-0.8 eV were present, with the latter pinning the Fermi level. Low temperature photocapacitance and capacitance voltage measurements of illuminated samples indicated the presence of high densities (10(17)-10(18) cm(-3)) of deep acceptors with an optical ionization threshold of 2.3 eV. Optical deep level transient spectroscopy (ODLTS) and photoinduced current transient spectroscopy (PICTS) detected electron traps at E-c-0.8 eV and E-c-1.1 eV. For lightly doped layers, the compensation of film conductivity was mostly provided by the E-c-2.3 eV acceptors. For heavily Sn doped films, deep acceptor centers possibly related to Ga vacancies were significant. The photocapacitance and the photocurrent caused by illumination at low temperatures were persistent, with an optical threshold of 1.9 eV and vanished only at temperatures of similar to 400 K. The capture barrier for electrons causing the persistent photocapacitance effect was estimated from ODLTS and PICTS to be 0.25-0.35 eV. Published by AIP Publishing.