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 VSi 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/cm2). 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 E2 (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.