In this work, we investigated the temperature-dependent photodetection behavior of a high-performance AlGaN/GaN-based ultraviolet phototransistor (UVPT) operating under 265 nm illumination. As the temperature continuously rises from room temperature to 250 °C, the photocurrent of a device increases in the beginning but suffers from degradation afterwards. This can be explained by the competing process between the generation and recombination rate of photo-induced carriers in the UVPT at room and high temperatures. Intriguingly, we found that the optimal operating temperature for our UVPT is around 50 °C, featuring a high peak responsivity of 1.52 × 105 A/W under a light intensity of 45  μW/cm2. Furthermore, the photoresponse time of our UVPT is also highly temperature-dependent, exhibiting the shortest rise time of 50 ms at 100 °C while the decay time is monotonically reduced as the temperature rises to 250 °C. Notably, our AlGaN/GaN-based UVPTs exhibit ultra-high responsivity at high temperatures, which have outperformed those earlier reported UV photodetectors in the form of different device architectures, highlighting the great potential of such device configurations for harsh environment applications.

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In this work, the effect of in situ SiNx grown with different carrier gas on the structural and electrical properties of the SiNx/AlGaN/GaN MIS-HEMTs is studied. It was found that the growth rate of SiNx grown with N2 as carrier gas (N2-SiNx) is more sensitive to different growth conditions, while the growth rate of SiNx grown with H2 as carrier gas (H2-SiNx) is very stable due to the inhibiting effects of H2 carrier gas on the SiH4–NH3 forward reactions. More importantly, a continuous and smooth SiNx growth at the initial stage can be realized with H2 carrier gas due to its faster surface migration, leading to a decent surface morphology and sharp interface of H2-SiNx. As a result, the SiNx passivated device with H2 as carrier gas shows improved performance compared to that with N2 as carrier gas, featuring ultra-low interface-state density of 2.8 × 1010 cm−2 eV−1, improved on- and off-state current, reduced threshold voltage shift, and mitigated current collapse, especially after long-term electrical stress. These results not only elaborate on the growth mechanisms of in situ SiNx with different carrier gases but also highlight the advances of H2 as carrier gas for in situ SiNx growth, providing an effective strategy to tailor the passivation schemes for GaN-based devices.