Starting layer dependence of the atomic-layer-deposited HfAlOxfilms on GaAs

This study reports the effects of the starting layer on the interface and electrical properties of HfAlOx films on GaAs, when the atomic layer deposition (ALD) was performed with tetrakis(ethylmethylamino)hafnium and trimethylaluminum precursors as well as an H2O oxidant. By using the Al2O3-first process, more decrease in the number of Ga–O bonds near the interface region was achieved than by using the HfO2-first process, which resulted in a reduction of the interface state density and the frequency dispersion. Furthermore, the Al2O3-first process decreased the border trap density, as well as the voltage stress-induced electron trapping, as estimated from the hysteresis characteristics of the capacitance–voltage and the leakage current measurement under a ramped-voltage stress condition. Based on these results, we experimentally demonstrate the importance of the cycling sequence during the ALD-HfAlOx process on GaAs.