Investigation Of Low-temperature Characteristic Of AlGaN/GaN Structure

Temperature reliability is an important aspect of HEMT reliability research. Peoplehave already made plenty of experiments and studies about the characteristics andreliability of AlGaN/GaN HEMT devices under high temperatures, and themeasurement method and analysis of the results has become more mature relatively.However, experiments and analysis under low temperature always appears to be rare,about which this article especially studies.Magnetotransport measurements were taken on the AlGaN/GaN on SiCheterostructures. The carrier concentration and mobility were obtained. Shubnikov-deHaas oscillations were observed in magnetic fields as low as4T at4.2K. By themeasurements and analysis of the temperature-dependent SdH oscillations, muchindispensable information of2DEG was extracted. The quantum Hall plateaus wereobserved, and the effective mass and quantum scattering time of the2DEG wasdetermined.The AlGaN/GaN HEMT device of1μm gate-length and100μm gate-width wasmade, whose electrical properties from300K to88K was measured then. The saturationdrain current increases obviously as the temperature decreases. The scatteringmechanism on the surface and interface of AlGaN/GaN heterostructures at lowtemperature changed greatly, improving mobility of2DEG. Threshold voltage driftsnegatively slightly. The reason is that Schottky barrier height deceases with fallingtemperature, which enhances the probability of electron tunneling and finally improvesthe Schottky current.At the same time, the AlGaN/GaN HEMT device also presents lower channelon-resistance, lower output conductivity, higher transconductance, and more obviouskink in output curves. The latter is affected mainly by source and drain series resistanceunder low temperatures.