Abstract
In this thesis, a novel light-emitting HEMT on AlGaN/GaN epitaxial layers on Si substrate were fabricated. This study is focused on light-emitting positions, distribution and wave length modulation with different light emitting GaN epitaxial layers, current conducting layers and p-type ohmic contacts. Devices on three kinds of epitaxial layers with the same fabrication process were investigated in this study: (A) a 20 nm Al0.25Ga0.75N/GaN HEMT on Si wafer with a 50 nm pGaN cap layer. (B) a 20 nm Al0.32Ga0.68N/Al0.07Ga0.93N HEMT on Si wafer with a 50 nm pGaN cap layer. (C) a 10 nm Al0.25Ga0.75N/GaN HEMT on Si wafer with a 50 nm pGaN cap layer. The observed lowest specific on-resistance among the LE-HEMTs structure is 22 mΩ-cm2 and the highest drain saturation current is 334 mA/mm on Sample A. For the on-state characteristics, the turn-on voltage (Vturn-on) can be improved from 6 V to 4.5 V by using Ni/Au/ITO as the p-type contacts. For optical properties, we try to study light emitting patterns by different mask layout designs. The wavelength of the emitted light is 364.42 nm on Sample A and 352.27 nm on Sample B, indicating the modulation of wavelength by the epitaxial structures. The extracted characteristic length of the light distribution is 38.4 μm on Sample A and 20.7μm on Sample C, respectively, from images captured by a CCD camera.