The Study Of Carrier Lifetime Enhancement Of 4H-SiC

At present, there is a hot spot problem in the application of Si C bipolar devices in the field of ultrahigh voltage?UHV? power devices, that is, the carrier lifetime of Si C materials.4H-Si C has superior properties such as wide band gap, high critical electric field strength, and high thermal conductivity, which make it an excellent candidate for higher-power and high-temperature semiconductor devices.Conductivity modulation in the drift layer of 4H-Si C bipolar devices determines the forward voltage drop and strongly depends on the carrier lifetime of the layer,That is, the longer the lifetime of 4H-Si C,the greater the conductivity modulation effect of the material. However, It is widely accepted that the Z_1/2 defect is the main lifetime limiting defect in the 4H-Si C material. Thus,In order to make ultrahigh-voltage bipolar devices have a smaller state losses and lower forward voltage drop, reducing the main lifetime limiting defect Z_1/2 and enhancing the carrier lifetime of 4H-Si C have become more and more important.Currently, there are several popular techniques to reduce the main lifetime limiting defect Z_1/2 in the 4H-Si C,such as C?carbon? or Si?silicon? ion implantation, high temperature thermal oxidation and surface passivation treatment and so on.In this paper, we mainly make carbon implantation in the 4H-Si C epitaxial films. The effect of carbon implantation on the epilayer of 4H-Si C and the characteristics of 4H-Si C Pi N diodes with carbon-implanted drift layer was investigated and studied.Firstly,The energies and doses of carbon implantation in the experiment were simulated by Silvaco semiconductor simulation software. According to the simulation results,The optimized implantation energies and doses are 80 ke V,120 ke V and 5×1014cm-2, 9×1014 cm-2,respectively,with 200 nm implantation mask of Si O2 layer.Secondly, testing and analyzing the carbon implanted 4H-Si C epilayer sample by using DLTS?deep level transient spectroscopy?, the results show that the concentration of mian lifetime limiting defect Z_1/2 in the carbon implanted 4H-Si Cepilayer was significantly decreased, and the carrier lifetime of the epilayer was enhanced.Finally,The forward I-V and reverse I-V characteristics of 4H-Si C Pi N diodes with carbon-implanted drift layer were studied.The forward I-V characteristics showed that carbon-implanted Pi N diodes had a typical forward voltage drop of around 3.3 V,which was much lower than that of the diodes fabricated by standard process. The differential on-resistance of the carbon-implanted Pi N diodes was 4.38m?·cm2@100A/cm2, which decreased about 50% compared with the Pi N diodes with standard process. For carbon-implanted Pi N diodes, the forward characteristics at temperatures ranging from 25? to 180? have also been obtained, the forward voltage drops decreased with an increase of temperature. And the reverse leakage current also decreased according to the reverse I-V characteristics of 4H-Si C Pi N diodes with carbon-implanted drift layer. As such, we concluded that the reduction of Z_1/2 traps can achieve longer carrier lifetime in drift layer, which can improve the characteristics of bipolar devices.