Zr doping in pulsed-laser-deposited α - Ga2O</mml:mrow…

The feasibility of zirconium doping of α-Ga₂O₃ grown by pulsed laser deposition is demonstrated. Targets with different zirconium contents are used to adjust the zirconium content in the thin films. Therefore, a two-step growth process is utilized, where first an undoped α-Ga₂O₃ thin film is grown as a high-temperature buffer layer and the zirconium-doped α-Ga₂O₃ layer is subsequently deposited at a lower growth temperature. Highly conductive thin films are obtained with resistivities as low as 3.3×10^-30.2em0exΩ0.2em0excm. An electron mobility as high as 380.2em0excm²0.2em0exV^-10.2em0exs^-1 is measured for a high free carrier density of 6.5×10¹⁸0.2em0excm^-3. The crystallization in the α-phase was confirmed by x-ray diffraction measurements. Further, a strong influence of the growth temperature on the zirconium incorporation is observed, which can be explained by the increased desorption of volatile Ga₂O₃ suboxides at high growth temperatures. Depth-resolved x-ray photoelectron spectroscopy measurements were employed to investigate the doping profile in the thin films. They reveal a strongly depth-dependent incorporation of the zirconium, with a decreased incorporation towards the surface. First Schottky barrier diodes on zirconium-doped α-Ga₂O₃ thin films with rectification ratios as high as 8.5 orders of magnitude at ±30.2em0exV are presented.