Improved Ga2O3 films on variously oriented Si substrates with Al2O3 or HfO2 buffer layer via atomic layer deposition

Abstract

Ga₂O₃ is an ultrawide-band-gap semiconductor with excellent properties and promising applications in the electronic and optoelectronics. For acting as the substrate for heteroepitaxial Ga₂O₃ films, Si has the advantages of wafer-level size, cheap price and nice compatibility whereas also perform the disadvantage of large thermal mismatch. In this paper, the apparent flower-like defects are exhibited on the macroscopic surfaces of annealed Ga₂O₃ films deposited on (100), (110) and (111) oriented Si substrates by atomic layer deposition (ALD) method. The reason is ascribed to the different thermal expansion coefficients between Ga₂O₃ and Si induced compressive and tensile stresses. The Al₂O₃ or HfO₂ buffer layer intercalated between Ga₂O₃ films and Si substrates via successive ALD process suppress the flower-like defects effectively while the surface roughnesses are low to be 1.290 nm and 2.393 nm, respectively. XRD spectra demonstrate that buffer layer indeed relieves the stress of Ga₂O₃ films on Si substrates while the amorphous Al₂O₃ has better influence than the polycrystalline HfO₂. The results are helpful to the improvement of growth quality and device property of Ga₂O₃.