Characterization and Control of GaN-based semiconductor interfaces for Fabrication of Field Effect Transistors

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Interface properties of metal/GaN, insulator/GaN, and AlGaN/GaN heterostructure have been characterized for the fabrication of MESFET and HEMT devices.1. Characterization of metal/GaN interfaces ; (1) Measured I-V-T and C-V-T characteristics for various metal/n, p-GaN schottky diodes, which include the Richardson plots together with temperature dependences of the effective schottky barrier height (SBH) and the ideality factor, can be consistently explained by the previously proposed "surface patch" model. Only the fraction of the total patchy area of 10^<-5>effectively reduces the SBH at RT, while it does not affect the flat-band SBH deduced from the C-V curve. (2) The true SBHs determined from high-temperature I-V curve are weakly dependent on the metal work function with small S-values of 0.28 for n-and p-GaN samples, respectively. (3) Although the effective SBH for a metal/n-AlGaN sample is considerably lowered at RT, owing to a tunneling current, the true SBH is fairly larger as compared with that for corresponding metal/GaN sample.2. Control of Metal/GaN Interface ; I-V characteristics are greatly improved by an annealing in nitrogen. Thermal oxidation of GaN surface leads to increase of the SBH without noticeable degradation of the diode characteristics.3. Simulation of GaN growth ; A Monte Carlo simulation program for MBE-GaN growth, which incorporates formation of anti-site defect of layer, was developed, and the influence of growth conditions on the flatness of the growth front surface and on defect density was examined.4. Characterization of deep levels ; Capture cross-sections and activation energies for bulk traps and interface states at SiO_2/GaN were determined by C-t measurements.5. Characterization of AlGaN/GaN heterostructures ; (1) Electrical properties of AlGaN/GaN heterostructures were systematically revealed by I-V-T and C-V-T measurements. (2) A new anodic etching process has been developed for the fabrication of HEMT devices.