Gallium nitride nanowire by nitridation of electrochemically grown gallium oxide on silicon

Abstract

GaN is a wide bandgap semiconductor with superb thermal, chemical, mechanical and electrical properties which makes it suitable for high power electronic and optoelectronic devices. Si substrate is preferable for the heterostructure growth of GaN due to its availability in large wafer size, low price and maturity. The co-integration of GaN-based devices on Si is very attractive towards the realization of advanced heterogeneous integration . A transformation of the grown Ga2O3 structures on Si to GaN by a so-called nitridation process is considered as a simple method to create a GaN/Si heterostructure. In the first stage, a synthesis of ß-Ga2O3 nanostructures on Si substrate by electrochemical deposition using a mixture of Ga2O3, HCl, NH4OH, and H2O was performed. The morphologies strongly depended on the molarity of Ga2O3 and pH level of electrolyte. ß-Ga2O3 nanodot-like structures were grown at low molarity of Ga2O3. However, Ga2O3 nanodot structures covered with nanorods on top of their surfaces were obtained at higher molarity, and the densities of nanorods seem to increase with the decrease of pH level. In the next stage, the nitridation of the electrodeposited Ga2O3 was performed. The complete nitridation was achieved at temperature of 900°C. Here, several prominent diffraction peaks correspond to hexagonal GaN (h-GaN) planes were detected with no diffraction peak of Ga2O3 structure. Temperature is a key parameter in a nitridation process where the deoxidization rate of Ga2O3 to generate gaseous Ga2O increase with temperature. It was found that a complete transformation cannot be realized without a complete deoxidization of Ga2O3. A significant change of morphological structures takes place after a complete transformation of Ga2O3 to GaN where the original nanorod structures of Ga2O3 diminish, and a new nanowire-like GaN structures appear. The studied method seems to be promising in producing high-quality h-GaN nanostructures on Si.