Operation Up to 500 °C of Al_0.85Ga_0.15N/Al_0.7Ga_0.3N High Electron Mobility Transistors

Abstract

AlGaN channel high electron mobility transistors (HEMTs) are the potential next step after GaN channel HEMTs, as the high aluminum content channel leads to an ultra-wide bandgap, higher breakdown field, and improved high temperature operation. Al 0.85 Ga 0.15 N/Al 0.7 Ga 0.3 N (85/70) HEMTs were operated up to 500 • C in ambient causing only 58% reduction of dc current relative to 25 • C measurement. The low gate leakage current contributed to high gate voltage operation up to +10 V under V ds = 10 V, with I ON /I OFF ratios of > 2 × 10 11 and 3 × 10 6 at 25 and 500 • C, respectively. Gate-lag measurements at 100 kHz and 10% duty cycle were ideal and only slight loss of pulsed current at high gate voltages was observed. Low interfacial defects give rise to high quality pulsed characteristics and a low subthreshold swing value of 80 mV/dec at room temperature. Herein is an analysis of AlGaN-channel HEMTs and their potential future for high power and high temperature applications. INDEX TERMS AlGaN, GaN, high electron mobility transistor (HEMT), high temperature.

Development and Modelling of Gallium Nitride Based Lateral Schottky Barrier Diodes with Anode Recesses for mmWave and THz Applications

“… = ideality factor; this is a mathematical correction factor added to rectify the diode current nonidealities that arise from practical defects, such as imperfections in the active layer caused by crystal structure damage during the growth process or a contamination within the various fabrication steps affecting the Schottky behavior of the anode. Ideally, its value should be a unity; however, for GaN material, the ideality factor ranges between 1.5 and 2.5 and higher in some cases [ 7 , 8 , 9 , 10 ].…”

“…To analyze these findings further, the semilog I - V plot (shown in Figure 10 ) is used, which allows the extraction of η n and Φ bh . Based on the analytical equations indicated in [ 8 ], both device structures exhibited η n between 1 and 2, indicating the presence of conduction mechanism besides a thermionic emission mechanism. An improvement of 14.28% in η n (from 1.97 to 1.69) was obtained by the developed multi-channel structure as compared to conventional SBDs.…”

Ultrawide bandgap Al x Ga1–x N channel heterostructure field transistors with drain currents exceeding 1.3 A mm−1

“…The fundamental reason for this is the alloy scattering which leads to the two-dimensional electron gas (2DEG) mobility in UWBG AlGaN channel layers approximately a factor of 3-5 lower than that of GaN. [10][11][12] Thus, the sheet resistance values for UWBG AlGaN channel HFETs are typically 2000 Ω/□ as compared to around 300 Ω/□ for GaN channel devices. [13][14][15] Another current limiting factor is the difficulty in forming formation of low resistivity ohmic contacts to UWBG AlGaN layers.…”

Proton Irradiation of High Aluminum Content AlGaN Polarization Doped Field Effect Transistors

“…10 Additionally, high temperature operation at 500 °C has been a focus of study with the devices operating with near-ideal characteristics at 100 kHz with full pinchoff. 11 The benefit of shifting from a heterojunction which was used in the aforementioned works, is that the POLFET avoids issues of interfacial roughness, simplifies Ohmic contact formation, and prevents carrier freeze-out at extreme low temperature operation. [12][13][14] This polarization doped field effect transistor has been previously well-characterized with elucidation on band structure and fabrication in an earlier work.…”