Effects of Charge Bump on High-Frequency Characteristics of α-SiC-based Double-drift ATT Diodes at Millimeter-wave Window Frequencies

Abstract

Extensive simulation experiments have been carried out on the DC and high-frequency characteristics of α-(4H) Silicon Carbide based double-drift (p++ p n n++ type) impact avalanche transit time (IMPATT) diodes at two important millimeter-wave window frequencies (35 and 140 GHz). The studies reveal that the IMPATT diode designed at Ka-band (at around 35.0 GHz) may yield an RF power density of 10.72 × 1012 Wm−2 with an efficiency of 21.5%, whereas the D-band (at around 140.0 GHz) IMPATT is capable of delivering an RF power density of 0.38 × 1012 Wm−2 with an efficiency of 15.0%. These results are very encouraging to choose SiC as a suitable base material for developing high-power and high-frequency IMPATT diodes. Impurity charge spikes are introduced in the flatly doped n and p regions of the double-drift diodes in the form of single low-high-low (p++ p p+ p n n+ n n++ type) bump. The effects of this charge bump on the mm-wave characteristics of the double-drift 4H-SiC IMPATTs are analyzed for the first time, through a modified simulation technique. It is interesting to note that the introduction of charge spikes improves the overall performance of the designed diodes at the window frequencies.