Base Ni/au Gan Schottky Contact Simulation And Experimental Research

GaN has wide, direct band gap, high breakdown field and high electron saturation velocity. These properties make GaN an ideal candidate for high power, microwave devices and ultra-violet(UV) photodetectors manufacturing. A high quality Schottky contact is a key factor to the devices. However Schottky contacts on GaN and AlGaN/GaN hetero-structure material are studied little in our country. So in the dissertation, Schottky contacts on n-GaN and AlGaN/GaN hetero-structures are studied in detail. The major achievements are listed.First, we established a two dimensions numerical simulation to analyze the electric properties and optimize the structures of the devices and simulated the electric properties of the device with various carrier concentrations, various temperatures and various interface layer thickness.Second,the transport mechanism of Schottky diodes fabricated on n-GaN is investigated by the temperature-dependent current-voltage measurements and temperature-dependent capacitance-voltage measurements, based on the classical theory of the electrical current transport mechanism. The experiment results show that there are different mechanisms under the different temperatures and bias. We gave a modified I-V characteristic formula and approved it coincided with the experiment results. The Schottky barrier highs determined from high-temperature I-V curves and low-temperature C-V curves is the same result from the metal work function. The effects of interface oxides thickness and Si concentration of the GaN on Schottky contact are also investigated. The experiment results indicated that the increase of Si concentration will lead to the degradation of Schottky contact, so the best value of Si concentration is 1017cm-3. Keeping the surface oxide is of benefit to the fabrication of Schottky contacts.Last, the temperature-dependent current-voltage measurements and temperature dependent capacitance-voltage measurements for Schottky diodes fabricated on AlGaN/GaN are studied. We compare the Schottky barrier highs and ideal factor of the Ni/Au-n-GaN and the Ni/Au-AlGaN/GaN in different temperatures. We also explain the meaning of the tested C-V curves, and according to this curves, we calculate the distributing of the 2DEG.