Copper-based p-type semiconducting oxides: from materials to devices
Joao Resende, PhD student, Laboratoire des Matériaux et du Génie Physique (LMGP), Université Grenoble Alpes.
Copper-based oxides presents promising electrical, optical and manufacturing features that establish this family of materials suitable for p-type transparent semiconductors applications. The work here presented focuses on the integration of Mg-doped Cu2O and CuCrO2 into pn junction devices, such as solar cells or UV photodetectors.
On a first study, we achieved the incorporation of magnesium in cuprous oxide grown by aerosol-assisted metal-organic chemical vapour deposition. The fabricated doped thin films reached up to 17% of magnesium, resulting in morphology changes. Electrical resistivity was reduced down to values as low as 6.6 W.cm, due to the increase of charge-carrier density. The presence of the dopant also lead to an increase of stability of the Cu2O phase under different annealing treatments, preventing the formation of CuO. Later, Mg-doped Cu2O was used for pn junctions showing a diode-like behavior, which can enable fast, scalable and cheap technology aiming for oxide based solar cells.On a second study, we demonstrate the first fabrication of ZnO / CuCrO2 core-shell nanowire heterostructures using low-cost, surface scalable, easily implemented chemical deposition techniques at moderate temperatures, and their integration into self-powered UV photodetectors. A 35 nm-thick conformal CuCrO2 shell with the delafossite phase and with high uniformity is formed by aerosol-assisted chemical vapor deposition over an array of vertically aligned ZnO nanowires grown by chemical bath deposition. The CuCrO2 shell consists of columnar grains at the top of ZnO nanowires as well as nano-grains with preferential orientations on their vertical sidewalls. The ZnO / CuCrO2 core-shell nanowire heterostructures present a significant rectifying behavior, with a maximum rectification ratio of 5500 at ±1V, as well as a high absorption above 85% in the UV region. When applied as self-powered UV photodetectors, the resulting optimized heterojunctions exhibit a maximum responsivity of 187 µA/W under zero bias and at 374 nm as well as a high selectivity with a UV-to-visible (374-550 nm) rejection ratio of 68 under an irradiance of 100 mW/cm2. These findings establish the present heterostructures consisting of ZnO nanowires covered with a semiconducting copper-based compound as a shell as a promising cost-efficient, all-oxide self-powered UV photodetector.
Date of update September 14, 2017