Résumé
u We report the results of combined investigations of as-grown stacking faults found in a-thick, undoped, 4H-SiC epitaxial layer grown by CVD. We have use successively, low temperature photoluminescence (LTPL), room temperature cathodo-lurninescence (RT-CL), micro-Raman (mu-R) and low temperature cathodo-luminescence (LT-CL) spectroscopy. From LTPL we find that the defects behave like thin, 2-dimensional, quantum wells made of 4 bilayers of the 3C polytype embedded in the 4H-SiC matrix. From RT-CL, we show that the faults have a triangular shape with a large extension in the basal plane and a maximum emission wavelength centered at about 480 nm at 300 K. This makes them intermediate between the usual (semi-infinite) QWs and the pure (1-dimensional) quantum dots. To confirm the 3C character of the SFs, we used mu R. Finally, using LT-CL we scanned across one single (isolated) triangular defect and found that the maximum signal wavelength shifts, depending on the exciting spot position over the defect. To the best of our knowledge, this constitutes the first experimental evidence of a screening of the built-in electric field when increasing the carrier concentration in the well. (c) 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.