Cu2O as hole injection layer on In-rich InGaN nanowires

We demonstrate the feasibility of p-type Cu2O as a hole injection/collection layer on low-bandgap In-rich InGaN nanowires (NWs). This overcomes the difficulty of p-type doping of In-rich InGaN and the use of wide-bandgap low-In-content p-type InGaN layers. The n-type InGaN NWs with 45% In content are grown by plasma-assisted molecular beam epitaxy and the Cu2O layers on top are fabricated by electrodeposition at low temperature. The Cu2O/InGaN heterostructure is characterized by x-ray diffraction, scanning electron microscopy, energy dispersive x-ray spectroscopy, transmission electron microscopy, Raman spectroscopy, photoluminescence spectroscopy, and current-voltage measurements. For sufficient Cu2O deposition amount to form a fully coalesced, compact layer and optimized Cu2O deposition temperature of 35 °C, the current-voltage curve shows a clear rectifying behavior with a rectification ratio close to 5 at ±3 V and turn-on voltage of 1.45 V. This reveals the successful hole injection from p-type Cu2O into n-type In-rich InGaN, but the obviously still high interface state density requires further improvement.