Formation of indium-tin oxide ohmic contacts for β-Ga2O3

Abstract

Sputter-deposited indium-tin oxide (ITO) electrodes became ohmic contacts for unintentionally doped β-Ga2O3(010) substrates with a carrier concentration of 2 × 1017 cm-3 after rapid thermal annealing in a wide range of annealing temperatures of 900-1150 °C. The formation of an ohmic contact is attributed to interdiffusion between ITO and β-Ga2O3, as evidenced by the results of transmission electron microscopy and energydispersive X-ray spectroscopy. The interdiffusion decreases the band gap and increases the donor concentration of β-Ga2O3 at the interface, and forms an intermediate semiconductor layer desirable for carrier transport. The ITO ohmic contact is particularly useful for future β-Ga2O3 devices operated at high temperatures.