Narrow Results

Plasma-assisted molecular beam epitaxial growth of Mg-doped GaN and InGaN on a sapphire substrate is investigated in this study. Electrical characteristics of p-type GaN strongly depend on the flux of Mg acceptors and the growth temperature. Only the intermediate range of Mg fluxes (beam equivalent pressures near 1×10^-9T) produce p-type GaN with good electrical properties, and a maximum hole concentration of 3.5 × 10¹⁸ cm^-3 is obtained with a Hall mobility of 2.1 cm²/V·s. Due to the strong surface accumulation of electrons, Hall measurements do not indicate p-type polarity for In fraction beyond 11%. In contrast, hot probe measurements show that p-polarity can be measured for the entire range of Mg-doped In mole fractions. Electroluminescence also indicates p-polarity for Ga-rich mole fractions. In_xGa_1-xNp-n homojunctions are fabricated and tested. All GaN devices show low series resistance (0.03 ohm-cm²) and insignificant parasitic leakage. IV curves of all three InGaN homojunctions show rectifying characteristics under dark conditions and photo-response under outdoor sunlight, indicating the existence of holes in InGaN with up to 40% In content.

AlGaN/GaN-based heterostructure field-effect transistors (HFETs) with and without Mg-doped semi-insulating carrier confinement layer were simulated by using ISE TCAD software, respectively. The detailed study on the electrical properties of these samples was performed. The effect of inserting Mg-doped GaN layer on the source–drain (S–D) leakage current was investigated. Higher values of drain current and extrinsic transconductance were achieved with conventional HFETs (without Mg-doped). The source-to-drain (S–D) leakage current of conventional HFETs was also higher. However, the S–D leakage current was reduced with the insertion of the Mg-doped semi-insulating carrier confinement layer. Our results are in good agreement with the experimental results obtained by other researchers.