Temperature dependent performance of ITO Schottky contacts on β-Ga2O3

Abstract

Sputtered indium tin oxide (ITO) was used as a rectifying contact on lightly n-type (n ∼ 1016 cm−3) β-Ga2O3 and found to exhibit excellent Schottky characteristics up to 500 K, with no thermally driven degradation to this temperature. The barrier height extracted from current–voltage characteristics was 1.15 ± 0.04 eV at 300 K and 0.78 ± 0.03 eV at 500 K, with thermionic behavior of charge carriers over the image force lowered Schottky barriers dominating the carrier transport at low temperatures. The breakdown voltages were 246, 185, and 144 V at 300, 400 and 500 K, respectively. At 600 K, the diodes suffered irreversible thermal damage. The diode on/off ratio was >105 for reverse biases up to 100 V. At higher reverse voltage, the current shows an I ∝ Vn relationship with voltage, indicating a trap-assisted space-charge-limited conduction (SCLC) mechanism. We observed this SCLC relation when the reverse voltage was larger than 100 V for 300 and 400 K and at <100 V at 500 K. The ITO can also be used to make Ohmic contacts on heavily doped Ga2O3 suggesting the possibility of completely optically transparent power devices.