n-SnO_x as a Transparent Electrode and Heterojunction for p-InP Nanowire Light Emitting Diodes

Transparent electronics are rapidly evolving with the development of transparent conducting oxides (TCOs). This work investigates both the electrical and optical properties of n-type tin oxide (SnO_x) film, deposited at various levels of oxygen concentration using magnetron sputtering. The band alignment at InP–SnO_x interface is further studied and SnO_x deposited at various conditions is used to demonstrate InP nanowire (NW) light emitting diodes (LEDs) to understand the trade-off between absorption and resistance. It is found that the device with lower resistance but higher absorption outperforms in terms of output power. Emission from the devices consists of two peaks at room temperature due to conduction band-to-heavy hole band transition and conduction band-to-light hole band transition. Decreasing the operating temperature brings about quite a complex transition in all the devices, which consists of two additional peaks due to Zn acceptor level and zincblende/wurtzite (ZB/WZ) recombination at NW/substrate interface. At temperatures below 208 K, the emission peak from conduction band-to-light hole band transition quenches, however the emission peaks from Zn acceptor level and ZB/WZ recombination become prominent. This work lays the foundation for realizing a new generation of efficient transparent electrodes in conjunction with NWs, eliminating the complex epitaxial growth process optimization of NW shell growth, heterostructure and doping.