Controlled generation of photoemissive defects in 4H-SiC using swift heavy ion irradiation

Defects in SiC have shown tremendous capabilities for quantum technology-based applications, making it necessary to achieve on-demand, high-concentration, and uniform-density defect ensembles. Here, we utilize 100 MeV Ag swift heavy ion irradiation on n-type and semi-insulating 4H-SiC for the controlled generation of the defects that have attracted a lot of attention. Photoluminescence spectroscopy shows strong evidence of V Si emitters in semi-insulating 4H-SiC. Additionally, irradiation generates photo-absorbing centers that enhance the optical absorption, suppressing the luminescence intensity at higher fluences ( ions/cm(2)). In n-type 4H-SiC, irradiation drastically increases the inter-conduction band transitions, attributed to absorption from trap centers. A clear correlation is found between (i) loss in the intensity of E-2 (TO) Raman signal and the enhancement in absorbance at 532 nm and (ii) decoupling of the longitudinal optical phonon-plasmon coupled Raman mode and the reduction in carrier concentration. The optical bandgap decreases with irradiation fluence for semi-insulating 4H-SiC. This is attributed to the formation of disorder and strain-induced localized electronic states near the band edges.