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Al0.85Ga0.15N/Al0.70Ga0.30N High Electron Mobility Transistors with Schottky Gates and Large On/Off Current Ratio over Temperature

ECS Journal of Solid State Science and Technology

Baca, A.G.; Klein, Brianna A.; Allerman, A.A.; Armstrong, Andrew A.; Douglas, Erica A.; Stephenson, Chad A.; Fortune, Torben R.; Kaplar, Robert K.

AlGaN-channel high electron mobility transistors (HEMTs) are among a class of ultra wide-bandgap transistors that are promising candidates for RF and power applications. Long-channel AlxGa1-xN HEMTs with x = 0.7 in the channel have been built and evaluated across the -50°C to +200°C temperature range. These devices achieved room temperature drain current as high as 46 mA/mm and were absent of gate leakage until the gate diode forward bias turn-on at ~2.8 V, with a modest -2.2 V threshold voltage. A very large Ion/Ioff current ratio, of 8 × 109 was demonstrated. A near ideal subthreshold slope that is just 35% higher than the theoretical limit across the temperature range was characterized. The ohmic contact characteristics were rectifying from -50°C to +50°C and became nearly linear at temperatures above 100°C. An activation energy of 0.55 eV dictates the temperature dependence of off-state leakage.

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TYPE Journal Article YEAR 2017
DOIOSTI

Planar Ohmic Contacts to Al 0.45 Ga 0.55 N/Al 0.3 Ga 0.7 N High Electron Mobility Transistors

ECS Journal of Solid State Science and Technology

Klein, Brianna A.; Baca, A.G.; Armstrong, Andrew A.; Allerman, A.A.; Sanchez, Carlos A.; Douglas, Erica A.; Crawford, Mary H.; Miller, Mary A.; Kotula, Paul G.; Fortune, Torben R.; Abate, Vincent M.

Here, we present a low resistance, straightforward planar ohmic contact for Al0.45Ga0.55N/Al0.3Ga0.7N high electron mobility transistors. Five metal stacks (a/Al/b/Au; a = Ti, Zr, V, Nb/Ti; b = Ni, Mo, V) were evaluated at three individual annealing temperatures (850, 900, and 950°C). The Ti/Al/Ni/Au achieved the lowest specific contact resistance at a 900°C anneal temperature. Transmission electron microscopy analysis revealed a metal-semiconductor interface of Ti-Al-Au for an ohmic (900°C anneal) and a Schottky (850°C anneal) Ti/Al/Ni/Au stack. HEMTs were fabricated using the optimized recipe with resulting contacts that had room-temperature specific contact resistances of ρc = 2.5 × 10-5 Ω cm², sheet resistances of RSH = 3.9 kΩ/$\blacksquare$, and maximum current densities of 75 mA/mm (at VGATE of 2 V). Electrical measurements from -50 to 200°C had decreasing specific contact resistance and increasing sheet resistance, with increasing temperature. These contacts enabled state-of-the-art performance of Al0.45Ga0.55N/Al0.3Ga0.7N HEMTs.

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TYPE Journal Article YEAR 2017
DOIOSTIDOIOSTI

Al0.45Ga0.55N/Al0.30Ga0.70N high electron mobility transistors with Schottky gates and small subthreshold slope factor

Device Research Conference - Conference Digest, DRC

Baca, A.G.; Armstrong, Andrew A.; Allerman, A.A.; Klein, Brianna A.; Douglas, Erica A.; Sanchez, Carlos A.; Fortune, Torben R.

Emerging ultrawide bandgap semiconductor materials are logical candidates for applications that exploit the large critical electric field (EC) associated with these devices. For semiconductor devices, EC scales approximately as Eg2 5 [1]. With a 25% larger bandgap and an approximately 73% larger EC than GaN, Al0.3Ga0.7N-channel high election mobility transistors (HEMTs) might be viable candidates for harsh environment electronics or short wavelength photo-transistors. In either case, transistor quality factors such as minimal off-state leakage currents and subthreshold slope factor are important metrics.

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TYPE Conference Poster YEAR 2017
OSTIScopus
Results 51–75 of 80
Results 51–75 of 80