Karl D Hobart

Performance and Stability of Large-Area 4H-SiC 10-kV Junction Barrier Schottky Rectifiers

The forward and reverse bias dc characteristics, the long-term stability under forward and reverse bias, and the reverse recovery performance of 4H-SiC junction barrier Schottky (JBS) diodes that are capable of blocking in excess of 10 kV with forward conduction of up to 10 A at a forward voltage of less than 3.5 V (at 25degC) are described. The diodes show a positive temperature coefficient of resistance and a stable Schottky barrier height of up to 200degC. The diodes show stable operation under continuous forward current injection at 20 A/cm2 and under continuous reverse bias of 8 kV at 125degC. When switched from a 10-A forward current to a blocking voltage of 3 kV at a current rate-of-fall of 30 A/mus, the reverse recovery time and the reverse recovery charge are nearly constant at 300 ns and 425 nC, respectively, over the entire temperature range of 25degC-175degC.

Topside Nanocrystalline Diamond Integration on AlGaN/GaN HEMTs for High Temperature Operation

GaN high electron mobility transistors (HEMTs) performance is limited by increased channel temperature, particularly resulting from self-heating during high power operation. Topside nanocrystalline diamond (NCD) layers have been integrated on AlGaN/GaN (HEMTs) to improve thermal management. HEMTs with NCD heat-spreading layers exhibit a 20% decrease in peak channel temperature compared to reference HEMTs, measured by Raman thermography, as well as improved sheet carrier density, transconductance, sheet resistance, Hall mobility, on-state resistance, and breakdown voltage. A “gate after diamond” approach is implemented to improve the thermal budget of the deposition process while maintaining the integrity of the Schottky gate electrode in a scalable process. Processing improvements for integrating NCD-capping with the HEMT are being pursued, such as eliminating the SiNx passivation interlayer, such that the NCD film is directly on the AlGaN barrier, as well as a sacrificial gate process. Also, boron doped ...