We propose a high temperature annealing process in N2 ambience after N2O plasma treatment for AlGaN/GaN HEMT. The annealing process effectively improves the plasma treated surface condition and decreases the current collapse from 41.7% to 10.6%. The N2O plasma treatment is performed in a PECVD chamber and the followed high temperature annealing process is carried out at 800℃ for 20min in rapid temperature annealing (RTA) system. Compared to the devices with only N2O plasma treatment, the devices with an extra high temperature annealing process perform lower surface state density (2.51E+12 cm −2 eV -1 , △E from 0.353 eV to 0.413 eV; 5.38E+11 cm −2 , △E > 0.519 eV) and better dynamic characteristics.
Abstract-In this paper, a K-band ground-based hyperspectral microwave radiometer for atmospheric sounding is proposed, which improves the profile error and vertical resolution of moisture profiling under the high water vapor condition. The hyperspectral microwave radiometer (80 K-band spectral channels) can observe the rapidly changing weather with high sensitivity and accuracy of brightness temperature by using a stable high-speed receiver and an improved tipping calibration method. By combining several advantages of traditional microwave receiver, the MMIC receiver has good ultrawideband performance, high linearity, and short measuring time. Moreover, through correcting the calibration parameters of traditional tipping calibration, the proposed calibration method can increase calibration accuracy based on the radiative transfer equation in the atmosphere. Measurement results demonstrate that the radiometer achieves a sensitivity of 0.1 K for 2 s of integration time and an accuracy of better than 0.77 K. For the water vapor profile, the variational retrievals method is used to extract the redundant information under the microwave hyperspectral condition. Preliminary comparisons of measured water vapor profiles with traditional results show good improvement of the profile error and vertical resolution.
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