Preparation of β-CuGaO2 thin films by ion-exchange of β-NaGaO2 film fabricated by a solgel method

β-CuGaO2 is a wurtzite-derived phase that is promising for ferroelectric and photovoltaic applications. Its bandgap measured in the form of powders is about 1.5 eV and is direct according to density functional theory calculations, making it an appropriate solar light absorber. In this work, we describe our attempts to grow this complex phase by pulsed laser deposition (PLD) that resulted in growing mostly CuGa2O4 on various crystal substrates such as SrTiO3 (STO), Al2O3 (ALO), ZnO, and ZrO2:Y (9.5 mol%Y2O3) (YSZ). In contrast, β-CuGaO2 is obtained using ion-exchange of β-NaGaO2 film fabricated with a cost-efficient spin coating by solgel method, on substrates composed of a SiN film on c-Si (001) wafer. The potential of the different films obtained is discussed in view of photovoltaic applications using surface photovoltage under white light and surface photovoltage spectroscopy. While we show that β-CuGaO2 is a suitable photon absorber, we conclude that the fact that the films are discontinuous is detrimental for electronic transport and additional dopants must be inserted in this material to promote its optoelectronic properties and charge carrier transport.