N. Ramungul

SiC and GaN bipolar power devices

Abstract The present status of the silicon carbide and gallium nitride bipolar power semiconductor devices is reviewed. Several unipolar and bipolar figures of merit have been examined to demonstrate the potential performance gain to be obtained from silicon carbide and gallium nitride based power devices. Several conventional as well as novel device structures have been examined, some of which have already been demonstrated and others are in their early stages of development. Conventional silicon theory has often been found to be inadequate to explain the characteristics of silicon carbide. Appropriate modifications have been applied to investigate more complicated characteristics of silicon carbide devices.

Phosphorus-implanted high-voltage n/sup +/p 4H-SiC junction rectifiers

In this paper, we report the fabrication and characterization of phosphorus-implanted 4H-SiC n/sup +//p junction rectifiers. Sheet resistance measurements of the implanted layers indicated values as low as 160 /spl Omega///spl square/. The forward characteristics of these diodes obey a generalized Shockley-Noyce-Sah (SNS) multiple-trap recombination model with 4 shallow levels and 1 deep level. Close-to-ideal avalanche breakdown voltage with a positive temperature coefficient is observed. The high-level injection lifetime has been extracted to characterize the switching behaviour of these diodes.

Static and dynamic characteristics of a 1100 V, double-implanted, planar, 4H-SiC PiN rectifier

Implanted, high-voltage, planar junction rectifiers in 4H-SiC are fabricated using a deep boron implanted junction along with a shallow heavily doped layer created by co-implantation of aluminum and carbon. The fabricated junctions can block up to about 1100 V with low forward drop and low leakage current. The static and dynamic characteristics of these rectifiers have been investigated at both room temperature and high temperature.

Current-controlled negative resistance (CCNR) in SiC P-i-N rectifiers

This paper presents an experimental demonstration of a current-controlled negative resistance (CCNR) in the forward characteristics of 6H-SiC P-i-N rectifiers. These forward characteristics indicate that the poor electrical performance of SiC diodes arises because conductivity modulation is not yet established. The cause of this behaviour appears to be high defect densities and low minority carrier lifetime in the lightly doped drift region. N/sup +/P junctions exhibit excellent forward characteristics with forward drop of 2.8 V at 100 A/cm/sup 2/ and 3.9 V at 1000 A/cm/sup 2/ without entering the CCNR mode when traps have been filled prior to the measurement.