For the fabricated AlGaN/GaN high electron mobility transistors (HEMTs) with different Ohmic contact widths, the gate-channel electron mobility is obtained experimentally. Mobility curves show very different values and trends. This phenomenon is investigated with the scattering theory in AlGaN/GaN HEMTs. The reason for the different mobility curves is found to be attributed to the different polarization charge distributions at the AlGaN/GaN interface. The AlGaN/GaN HEMT with a smaller Ohmic contact width corresponds to positive additional polarization charge near the Ohmic contact. The AlGaN/GaN HEMT with a larger Ohmic contact width corresponds to negative additional polarization charge near the Ohmic contact. Changing the Ohmic contact width will be a new dimension to optimize the characteristics of AlGaN/GaN HEMTs effectively.

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AlGaN/GaN high electron mobility transistors (HEMTs) with different device sizes were prepared and suffered 0.4 MeV proton irradiation. The low-field carrier transport characteristics of the gate channel are obtained from capacitance-voltage curves and current-voltage curves. For the device with a longer gate-drain distance (30 μm), after 0.4 MeV proton irradiation, the gate-channel low-field carrier mobility increases by 14.3% averagely. For the device with a shorter gate-drain distance (15 μm), the carrier mobility decreases by 13.4% averagely after proton irradiation. This phenomenon is studied in the view of polarization scattering effect. It is found that the polarization distribution in the AlGaN/GaN HEMTs changes after proton irradiation, and different gate-drain distances correspond to different polarization distributions.

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