Characterization of Ge doped c-InGaN structures for photoelectrochemical water splitting

Impact of Ge-doping on the photoelectrochemical response of cubic (Ga,In)N photoelectrodes Institute of Experimental Physics I, Heinrich-Buff-Ring 16, 35392 Giessen (Ga,In)N is a promising electrode material for electrochemical water splitting as the amount of indium determines the band gap of the semiconductor alloy. In this study we focus on the influence of germanium doping on the photoelectrochemical response of cubic (In,Ga)N photoanodes, which were grown by molecular beam epitaxy (MBE). Different methods like open circuit potential, cyclic voltammetry and electrochemical impedance spectroscopy were used to analyse charge carrier transport and the properties of the electrode electrolyte interface, such as flat band potential. The non-intentionally doped samples show a high photocurrent, indicating less recombination and efficient charge separation, while Doping decreases the photoelectrochemical response. Despite the lower photocurrent, the doped samples show higher electrochemical stability displaying structural strength and chemical resistance at the interface. The results show that a trade-off between stability and activity needs to be achieved by controlling doping and indium concentration to develop durable and efficient III-nitride photoanodes for solar water splitting.