Chloride-hydride Vapor-phase Research Articles

Effect of Pretreatment of the Silicon Substrate on the Properties of GaN Films Grown by Chloride–Hydride Vapor-Phase Epitaxy

Effect of Pretreatment of the Silicon Substrate on the Properties of GaN Films Grown by Chloride–Hydride Vapor-Phase Epitaxy

Photoelectrochemical Corrosion of GaN/AlGaN-Based p-n Structures

Direct water photoelectrolysis using III-N materials is a promising way for hydrogen production. GaN/AlGaN based p-n structures were used as working electrodes in a photoelectrochemical process to investigate the material etching (corrosion). The structures were grown on sapphire substrates by chloride Hydride Vapor Phase Epitaxy (HVPE). First, the etching process occurs near vertically via channels associated with defects in the structure and penetrates deep into the structure. Then, the process involves etching of the n-type AlGaN barrier and n-GaN active layer in lateral direction resulting in formation of voids and cavities. The lateral etching is due to net positive charges at the AlGaN/GaN interfaces arising because of spontaneous and piezoelectric polarization in the structure and positively charged ionized donors in the space charge region of the p-n junction.

Photo-Electrochemical Etching in the Process of Direct H2 Generation by Illumination of GaN-Based Material Structures Immersed in Water

Hydrogen is considered a promising candidate for energy storage. We investigated the cleanest way for hydrogen production by direct photo electrolysis of water with GaN/AlGaN based p-n structures used as working electrodes. Besides the H2 production rate, an important consideration is the material etching (corrosion) that accompanies the photo-electrochemical process. The GaN-based structures were grown on sapphire substrates by the chloride hydride vapor phase epitaxy and used as a photo anode immersed into an aqueous electrolyte. For a p-n GaN/AlGaN structure we observed a H2 production rate of 0.6 mL/cm2×h. Corrosion of the electrode proceeds in two steps. First, there is a near vertical etching process, which is associated with defects in the material and penetrates deep into the structure. Subsequently, the process involves etching of n-type layers in lateral direction resulting in the formation of voids and cavities. The lateral etching is due to net positive charges arising from the spontaneous and piezoelectric polarization in the structure and positively charged ionized donors in the space charge region of the p-n junction.