Comparative analysis of static characteristics of insulated gate bipolar transistors and thyristors with static induction

Abstract

Two-dimensional numerical simulation of equivalent silicon insulated gate bipolar transistors (IGBT) and static induction thyristors (SITh) with a trench structure in the conductive and blocking states has been performed. Thickness d of the high-resistance n base was changed within 120–456 μm at donor concentrations N d = 7.0−1.75 × 1013 cm−3 and diffusion length of nonequilibrium charge carriers L = 0.25−1.0d. Comparative analysis of the results has shown that the blocking characteristics of the SITh and IGBT are almost the same but breakdown voltage U b varies in the range of 1.4–4.6 kV depending on d, N b , and L. The voltage drop in the conductive states in the IGBT without a stop layer is much larger than in the SITh. The superiority of the SITh increases with growth U b and with decreasing L. The reason for this is the relatively low injection efficiency of the cathode emitter of the IGBT, leading to a strong decrease in nonequilibrium charge carrier concentration near the cathode and a corresponding increase of the field strength. Introduction of an additional thin n-type stop layer between the base and the collector of the IGBT leads to significant weakening of the leakage of the holes. This improves the efficiency of injection and results in a significant increase of electron and hole concentrations and reduces the field strength in the half of the base of the IGBT that is nearest to the cathode. As a result, the voltage drops on the IGBT and SITh converge, especially with decreasing L and current density and with increasing U b . However, even in such a modified IGBT, concentration n is lower and the field strength is greater than in an SITh. Therefore, at current density J > 10 A/cm2, the SITh has a lower on-state resistance than the equivalent modified IGBT.