Transmission electron microscope radiation damage of 4H and 6H SiC studied by photoluminescence spectroscopy

Damage created by relatively low voltage electron irradiation of 4H and 6H SiC has been studied by low-temperature photoluminescence microscopy. The damage was created by a transmission electron microscope operated in the voltage range 80-300 kV. The samples were both n- and p-doped and a wide range of different irradiation conditions has been investigated with subsequent specimen annealing up to 1000 °C. A rich variety of spatial features was encountered using 325 nm, 488 nm and 514.5 nm laser excitation. These have been correlated between different polytypes to identify centres with similar properties. Use of voltage variation of the incident electrons has permitted a distinction to be made between damage related to Si displacement and that related to C displacements. Migration outside of the electron irradiation has been correlated with centres exhibiting characteristics typical of interstitial atoms, while vacancy-related centres remain within the region of electron irradiation itself. Mechanisms responsible for this outward migration of interstitials have been proposed.