Electrical properties of α-Ga2O3 films grown by halide vapor phase epitaxy on sapphire with α-Cr2O3 buffers

We report on growth and electrical properties of alpha-Ga2O3 films prepared by halide vapor phase epitaxy (HVPE) at 500 & DEG;C on alpha-Cr2O3 buffers predeposited on sapphire by magnetron sputtering. The alpha-Cr2O3 buffers showed a wide microcathodoluminescence (MCL) peak near 350 nm corresponding to the alpha-Cr2O3 bandgap and a sharp MCL line near 700 nm due to the Cr+ intracenter transition. Ohmic contacts to Cr2O3 were made with both Ti/Au or Ni, producing linear current-voltage (I-V) characteristics over a wide temperature range with an activation energy of conductivity of & SIM;75 meV. The sign of thermoelectric power indicated p-type conductivity of the buffers. Sn-doped, 2-mu m-thick alpha-Ga2O3 films prepared on this buffer by HVPE showed donor ionization energies of 0.2-0.25 eV, while undoped films were resistive with the Fermi level pinned at E-C of 0.3 eV. The I-V and capacitance-voltage (C-V) characteristics of Ni Schottky diodes on Sn-doped samples using a Cr2O3 buffer indicated the presence of two face-to-face junctions, one between n-Ga2O3 and p-Cr2O3, the other due to the Ni Schottky diode with n-Ga2O3. The spectral dependence of the photocurrent measured on the structure showed the presence of three major deep traps with optical ionization thresholds near 1.3, 2, and 2.8 eV. Photoinduced current transient spectroscopy spectra of the structures were dominated by deep traps with an ionization energy of 0.95 eV. These experiments suggest another pathway to obtain p-n heterojunctions in the alpha-Ga2O3 system. Published under an exclusive license by AIP Publishing.

Automated summary

This study reports on the growth and electrical properties of alpha-Ga2O3 films grown on alpha-Cr2O3 buffers using halide vapor phase epitaxy. The experimental results showed p-type conductivity of the buffers and low donor ionization energies in Sn-doped alpha-Ga2O3 films prepared on these buffers.