A Simple Method to Differentiate between Free-Carrier Recombination and Trapping Centers in the Bandgap of the p-Type Semiconductor

In this research, the ranges of the localized states in which the recombination and the trapping rates of free carriers dominate the entire transition rates of free carriers in the bandgap of the p-type semiconductor are described. Applying the Shockley–Read–Hall model to a p-type material under a low injection level, the expressions for the recombination rates, the trapping rates, and the excess carrier lifetimes (recombination and trapping) were described as functions of the localized state energies. Next, the very important quantities called the excess carriers’ trapping ratios were described as functions of the localized state energies. Variations of the magnitudes of the excess carriers’ trapping ratios with the localized state energies enable us to categorize the localized states in the bandgap as the recombination, the trapping, the acceptor, and the donor levels. Effects of the majority and the minority carriers’ trapping on the excess carrier lifetimes are also evaluated at different localized energy levels. The obtained results reveal that only excess minority trapping affects the excess carrier lifetimes, and excess majority carrier trapping has no effect.

Minority Carrier Lifetime Measurements on 4H-SiC Epiwafers by Time-Resolved Photoluminescence and Microwave Detected Photoconductivity

Temperature dependent microwave detected photoconductivity MDP and time-resolved photoluminescence TRPL were employed to investigate the carrier lifetime in CVD grown 4H-SiC epilayers of different thickness. The minority carrier lifetime may be found from both theMDP and defect PL decay at room temperature for all epilayers, whereas the near bandedge emission (NBE) decay is much faster for thin epilayers (<17 μm) due to the substrate proximity and only follows the minority carrier lifetime for thicker samples at lower excess carrier concentrations.

Local Lifetime Control in 4H-SiC by Proton Irradiation

The effect of local lifetime control by proton irradiation on the OCVD response of a 10 kV SiC PiN diode was investigated. Carrier lifetime was reduced locally by irradiation with 800 keV protons at fluences up to 1x1011cm-2. Radiation defects were characterized by DLTS and C-V profiling; excess carrier dynamics were measured by the OCVD and analyzed using the calibrated device simulator ATLAS from Silvaco, Inc. Results show that proton implantation followed by low temperature annealing can be used for controllable local lifetime reduction in SiC devices. The dominant recombination centre is the Z1/2defect, whose distribution can be set by irradiation energy and fluence. The local lifetime reduction, which improves diode recovery, can be monitored by OCVD response and simulated using the SRH model accounting for the Z1/2defect.