Low Hysteresis Dispersion La2O3 AlGaN ∕ GaN MOS-HEMTs

AlGaN/GaN metal-oxide-semiconductor high electron mobility transistors (MOS-HEMTs) using electron-beam evaporated high-dielectric-constant (high-k) lanthanum oxide layer (La 2 O 3 ) as the gate insulator have been investigated and compared with the traditional GaN HEMTs. The dielectric constant of the La 2 O 3 insulator layer developed in this study was 13.1. In addition, a negligible hysteresis voltage shift in the capacitance-voltage curves can be obtained after high temperature annealing. The compositions and the crystalline structures of La 2 O 3 with different annealing temperatures were observed by X-ray photoelectron spectroscopy and X-ray diffraction, respectively. The La 2 O 3 thin film achieved a good thermal stability after 200, 400, and 600°C postdeposition annealing owing to its high binding energy (835.7 eV) characteristics. Moreover, the gate leakage current of a traditional metal gate GaN HEMT can be suppressed for 1 order of magnitude after inserting a La 2 O 3 insulator between Ni and AlGaN, resulting in a better pulsed-mode operation. The device linearity was also improved due to its flat and wide transconductance (g m ) distribution, which was analyzed by a polynomial curve-fitting technique. Therefore, La 2 O 3 is a potential candidate high-k material for the gate insulator to enhance the GaN-based field effect transistor performance while scaling down the device dimension and device reliability at high power operation.

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