[TuP3C] Power Devices

[TuP3C-02] Distribution of Deep-Level Nonradiative Recombination Centers in 4H-SiC Investigated by Laser Heterodyne Photothermal Displacement Method

〇Kouyou Harada¹, Masashi Kato², Atsuhiko Fukuyama¹ (1. Univ. of Miyazaki (Japan), 2. Nagoya Inst. of Tech (Japan))

4H-SiC has been attracting much attention as a material for low-loss power devices. However, deep levels located within the bandgap significantly reduce carrier lifetime. In this study, we aimed to visualize the distribution of deep levels in 4H-SiC crystals using the Laser Heterodyne Photothermal Displacement (LH-PD) method, which enables highly sensitive and non-contact detection of nonradiative transitions. LH-PD mapping was also performed on commercially available N-doped n-type 4H-SiC substrates. Distinct striation patterns with a width of approximately 1 mm were observed in both cases, with the excitation energies below and above the band gap. Additional investigations using Polarized Light Microscopy and Raman Spectroscopy confirmed the absence of residual stress and constant nitrogen dopant concentration, effectively ruling out these factors as the origin of the LH-PD striation patterns. Since the same patterns were observed even under the below band gap excitation, the observed signals are due to the displacement induced by a nonradiative recombination via deep levels, which is distributed along growth striations formed during the physical vapor transport (PVT) growth process.