| dc.description.abstract | In this work, we focus on AlGaN/GaN HEMT with different cap layers which may influence on electrical property. We use three types of cap layers including conventional GaN cap,p-type GaN cap and in-situ SiN grown in the MOCVD. The purpose of this study is to improve device breakdown voltage and dynamic Ron. Material analysis is discussed before fabricating Schottky device.
Among the Schottky devices with different cap layers, in-situ SiN cap device has the lowest gate leakage current, high on/off current ratio 1.71×108, subthreshold slope at 82 mV/dec, and have the largest breakdown voltage about 1200V at LGD = 20 μm. In terms of dynamic Ron, p-GaN device and in-situ SiN device stressed at VDS = 100V show better results than GaN cap. The corresponding dynamic Ron ratio are 1.8 and 1.2, respectively. In addition, we use pulse measurement to investigate the surface trap in these three structure.
Finally, in this experiment we use substrate bias to separate device with the contributions of surface- and buffer-induced trapping effect. Among three structure, device with GaN cap show the worst performance, the current recovery to the steady state requiring longer time. The activation energy associated with the defects are analyzed by temperature-dependent dynamic Ron measurement.
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