N-polar GaN-based MIS-HEMTs for mixed signal applications
ABSTRACT GaN-based transistors are attractive for the next-generation RF power and mixed signal electronics due to their high breakdown field and high carrier saturation velocity. III-N high electron mobility transistors (HEMTs) fabricated on the N-face of GaN are well-suited to address the problems of poor electron confinement and high ohmic contact resistance in the highly scaled transistors. At 4 GHz, N-polar metal-insulator-semiconductor (MIS)-HEMTs with a gate length of 0.7 μm exhibited a highest output power density (Pout) of 8.1 W/mm and a highest power-added efficiency (PAE) of 71%, while a Pout of 4.2 W/mm and a PAE of 49% were achieved at 10 GHz. A high speed N-polar MIS-HEMT fabricated with a gate-first self-aligned InGaN-based ohmic contact regrowth technology was characterized, demonstrating an ultra-low contact resistance of 23 Ω-μm and a state-of-the-art fT·LG product of 16.8 GHz-μm with a gate length of 130 nm.
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ABSTRACT: In this paper, we report the recent progress in the high-frequency performance of enhancement-mode devices in the novel N-polar GaN technology and provide a pathway for further scaling. The intrinsic advantages of electron confinement, polarization doping of the back-barrier and the absence of a source barrier in N-polar GaN technology were leveraged with polarization engineering with a top barrier for enhancement mode operation and advanced self-aligned source/drain technology for low parasitic access resistances. The scalability of the device structures are explored in terms of short-channel effects and high-frequency performance. Low-field electron mobility in vertically scaled channel was also investigated providing insights on the scattering mechanism.Semiconductor Science and Technology 06/2013; 28(7):074006. · 2.21 Impact Factor