Characterization of different-Al-content AlGaN/GaN heterostructures and high-electron-mobility transistors grown on 100-mm-diameter sapphire substrates by metalorganic vapor phase epitaxy

Different-Al-content Al_xGa_1-xN/GaN (0.26 ≤ x ≤ 0.52) high-electron-mobility transistor (HEMT) structures were grown on large-area 100-mm-diameter sapphire substrates by metalorganic vapor phase epitaxy (MOVPE). A low sheet resistance of approximately 380 Ω/sq. and an in-wafer total variation of 7.6% with a standard deviation of 1.6% were obtained for the sample with the highest Al content of 0.52. The two-dimensional electron gas (2DEG) density and room-temperature Hall mobility of the Al_0.52Ga_0.48N/GaN HEMT structures were 1.76 × 10¹³/cm² and 971 cm²/Vs with in-wafer total variations of 7.8% and 8.1%, respectively. HEMTs were successfully fabricated and they exhibited good dc characteristics. The dependence of maximum source-drain current density on Al content was consistent with the Al content dependence of sheet carrier concentration. The highest source-drain current density of 1033 mA/mm with a maximum extrinsic transconductance of 228 mS/mm was obtained for 2-μm-gate-length Al_0.52Ga _0.48N/GaN HEMTs.