Recent advances in high temperature, high frequency SiC devices

Silicon carbide (SiC) is an emerging semiconductor which has proven to be well suited to high temperature power switching and high-frequency power generation. This paper examines recent advances in materials development and device performance. In boule growth, we have focused on increasing boule diameter and reducing defect counts. Two conductivity types have been developed: (1) undoped semi-insulating for MESFETs, and (2) nitrogen doped highly conducting boules for SITs and power switches. Very uniform planetary multiwafer epitaxial layer growth on these wafers is described, in which specular epitaxial layers have been obtained with growth rates of 3-5 μm/hr, exhibiting unintentional n-type doping of ~1×10¹⁵ cm^-3, and associated room temperature Hall mobilities of ~1000 cm²/Vs. Controlled n-type doping between ~5×10¹⁵ cm^-3 and >1×10¹⁸ cm^-3 has also been demonstrated using nitrogen doping. SiC finds application in high temperature power switching devices and microwave power transistors. MOS turn-off thyristors (MTO^TM) are being investigated as power switches because they offer ease of turn-off, 500°C operation and reduced cooling requirements. In the fabrication of high power, high frequency transistors at UHF, L-band, S-band and X-band, SiC has been found superior to both silicon and GaAs. For example, a 4H-SiC UHF television module has demonstrated good signal fidelity at the 2000 W PEP level, S-band transistors have shown 300 W peak power for radar applications, and 6 W power output has been obtained at X-band