Abstract
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.
Highlights
Hydrogen is considered a candidate as the substantial energy carrier
Several technologies are used or being developed for hydrogen generation using solar energy directly or indirectly. They include among others thermochemical water decomposition process driven by a concentrated solar system, generation of hydrogen through biomass, hydrogen production through photosynthetic microorganisms and hydrogen production by electrolysis (Turner et al, 2008)
The basic structure included a 50100 nm-thick GaN active region co-doped by Zn and Si to have emission at 420 nm (Usikov et al, 2003), which was sandwiched between p- and n- AlxGa1-xN barriers (x~0.05-0.12), all grown on a 2-3 μm thick n-GaN:Si contact layer (n~2-4×1018 cm–3)
Summary
Hydrogen is considered a candidate as the substantial energy carrier. In the process of hydrogen energy consumption, water, as the product of hydrogen oxidation, is harmless to the environment. Several technologies are used or being developed for hydrogen generation using solar energy directly or indirectly. They include among others thermochemical water decomposition process driven by a concentrated solar system, generation of hydrogen through biomass, hydrogen production through photosynthetic microorganisms and hydrogen production by electrolysis (Turner et al, 2008). In the latter case the electrolysis can be driven by renewable electricity and performs water decomposition electrochemically
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