AlGaInP-Based LEDs With Al-doped ZnO Transparent Conductive Layer Grown by MOCVD

Abstract

In this paper, Al-doped ZnO (AZO) grown by metal-organic chemical vapor deposition (MOCVD) using H2O as an oxidizer was employed as a transparent conductive layer (TCL) in AlGaInP-based light-emitting diodes (LEDs). A direct ohmic contact structure was observed between the AZO and the carbon-doped p+-GaP (p+-GaP:C) contact layer with a specific contact resistance of $\mathsf {2.2} \times \mathsf {10}^{{\mathsf {-4}}} $ cm $^{{\mathsf {2}}}$ . It is attributed to the unintentional hydrogen-doped n++-AZO interfacial layer at the clear interface of the AZO/p+-GaP:C. A forward voltage ( ${V}_{f}$ ) of 1.99 V at 20 mA was achieved, which is lower than that of the ITO-TCL LED with a ${V}_{f}$ of 2.07 V. In addition, compared with the conventional LED without TCL and the ITO-TCL LED, the studied LED demonstrates high output power and high wall-plug efficiencies. These results indicate that the AZO-TCL grown by MOCVD using H2O as an oxidizer is an effective current spreading layer for high-performance AlGaInP-based LED application.