Improved performance of InGaN/GaN LED by optimizing the properties of the bulk and interface of ITO on p-GaN

Abstract

Indium Tin Oxide films were deposited directly on p-type Gallium Nitride film using the electron beam deposition method at different substrate temperatures from 25 °C to 550 °C. The structural, optical and Hall measurements represent a direct correlation of ITO properties with the substrate temperature during deposition. The substrate temperature of 450 °C produces the best ITO/p-GaN properties for the InGaN/GaN Light Emitting Diode performance, which outperforms the 550 °C device, although the latter exhibits better optical characteristics. At 100 mA, the 450 °C LED exhibits the highest power efficiency of 9.32 mW with an operation voltage of 6.96 V. X-ray Photoemission Spectroscopy measurement shows that substitution of Sn4+ occurs inside the In2O3 structure, which reaches its limit at the 450 °C substrate temperature. This result manifests the crucial role of the surface chemistry effect on the current injection into the LED. Additionally, the band offset of ITO/p-GaN interface data shows that the interface of the 450 °C sample exhibits the highest conduction band offset of 1.93 eV. For the metal/ITO junction, the 450 °C sample experiences the lowest Conduction Band Maximum of 0.69 eV, which ultimately helps to enhance the carrier injection from the anode part in the device.