Long Photoconductivity Decay Characteristics in p-Type 4H-SiC Bulk Crystals

We investigated the photoconductivity decay characteristics of p-type 4H-SiC bulk crystals by differential microwave photoconductance decay (μ-PCD) measurements using a 349-nm laser as an excitation source. The decay time at room temperature was 2600 μs, which is much longer than that of n-type 4H-SiC bulk crystals (40 ns). Decay time decreased with increasing temperature, resulting in 120 μs at 250 °C, and the activation energy of decay time was determined to be $140\pm 10$ meV. Long decay characteristics were also observed by below-band-gap excitation at 523 nm.