Aluminum function in Al-doped HfGaO films deposited at low temperature

Highlight • A vapor cooling condensation system was utilized to deposit Al-doped HfGaO films. • The bandgap energy of AlHfGaO films could be modulated by adding Al dopants. • The oxygen vacancy in the AlHfGaO films could be suppressed by adding Al dopants. AlHfGaO films with various Al atomic contents were deposited on sapphire substrates at approximately 80 K by using a vapor cooling condensation system. Energy-dispersive spectrometer measurements revealed that increasing the deposition temperature of an Al2O3-powder-loaded tungsten boat increased the Al atomic content of the AlHfGaO films. AlHfGaO films with an Al atomic content of 3.16% had a higher optical bandgap energy (5.36 eV) than did undoped HfGaO films (5.14 eV). Increasing the Al atomic content reduced the Ga atomic content; however, the Hf atomic content was similarly unchanged, which revealed that the Al dopants substituted Ga atoms. X-ray photoelectron spectroscopy measurements indicated that the oxygen vacancy defects in HfGaO films were suppressed by doping with Al to produce AlHfGaO films. The results of this study verified that the Al doping of HfGaO films could effectively modify the bandgap energy and could suppress oxygen vacancy defects.