Combined investigations were made of as-grown stacking faults found in a thick undoped 4H-SiC epitaxial layer grown by CVD. Low-temperature photoluminescence, room-temperature cathodoluminescence, micro-Raman and low-temperature cathodoluminescence spectroscopy were used successively. From low temperature photoluminescence data, it was found that the defects behaved like thin 2-dimensional quantum wells made of 4 bilayers of the 3C polytype embedded in the 4H-SiC matrix. From room temperature cathodoluminescence data, it was shown that the faults had a triangular shape with a large extension in the basal plane and a maximum emission wavelength centred at about 480nm at 300K. This made them intermediate between the usual (semi-infinite) quantum wells and the pure (1-dimensional) quantum dots. To confirm the 3C character of the stacking faults, micro-Raman spectroscopy was used. Finally, using low temperature cathodoluminescence spectroscopy, scans were made across a single (isolated) triangular defect and it was found that the maximum signal wavelength shifted, depending upon the exciting spot position over the defect. This was thought to constitute the first experimental evidence of screening of the built-in electric field upon increasing the carrier concentration in the well.

Photoluminescence, Cathodo-Luminescence and Micro-Raman Spectroscopy of As-Grown Stacking Faults in 4H-SiC. S.Juillaguet, M.Albrecht, R.Lewandowska, J.Camassel, T.Chassagne: Physica Status Solidi C, 2007, 4[4], 1513-6