Excess Carrier Lifetime in a Bulk p-Type 4H–SiC Wafer Measured by the Microwave Photoconductivity Decay Method

Abstract

Excess carrier lifetime in a p-type 4H–SiC wafer was measured by the microwave photoconductivity decay (µ-PCD) method. The obtained excess carrier decay curve had the fast and slow components with time constants of ≤1 µs and ≥1 ms, respectively. The 1/e lifetime map for the wafer showed that the time constant of the fast component decreases around structural defects. On the other hand, the 1/e2 lifetime map showed that the time constant of the slow component does not depend on the defect distribution. We measured decay curves for the slow component at various temperatures, and fitted them to those obtained from the numerical simulation. The fitting result showed that the slow component is caused by a minority carrier trap located at 0.16 eV below the conduction band. From the measurement of samples with various surface conditions, we found that the excess carrier decay is independent of the surface condition. Thus, the excess carrier decay is caused predominantly by recombination in the bulk rather than at the surface of the wafer.