AlGaN/GaN on SiC Devices without a GaN Buffer Layer: Electrical and Noise Characteristics

We report on the high-voltage, noise, and radio frequency (RF) performances of aluminium gallium nitride/gallium nitride (AlGaN/GaN) on silicon carbide (SiC) devices without any GaN buffer. Such a GaN–SiC hybrid material was developed in order to improve thermal management and to reduce trapping effects. Fabricated Schottky barrier diodes (SBDs) demonstrated an ideality factor n at approximately 1.7 and breakdown voltages (fields) up to 780 V (approximately 0.8 MV/cm). Hall measurements revealed a thermally stable electron density at N(2DEG) = 1 × 10(13) cm(−2) of two-dimensional electron gas in the range of 77–300 K, with mobilities μ = 1.7 × 10(3) cm(2)/V∙s and μ = 1.0 × 10(4) cm(2)/V∙s at 300 K and 77 K, respectively. The maximum drain current and the transconductance were demonstrated to be as high as 0.5 A/mm and 150 mS/mm, respectively, for the transistors with gate length L(G) = 5 μm. Low-frequency noise measurements demonstrated an effective trap density below 10(19) cm(−3) eV(−1). RF analysis revealed f(T) and f(max) values up to 1.3 GHz and 6.7 GHz, respectively, demonstrating figures of merit f(T) × L(G) up to 6.7 GHz × µm. These data further confirm the high potential of a GaN–SiC hybrid material for the development of thin high electron mobility transistors (HEMTs) and SBDs with improved thermal stability for high-frequency and high-power applications.