Papers by Author: Takeshi Mitani

Abstract: Depth profiles of ion-implantation induced defect centers have been investigated by cross-sectional CL measurements in the energy range from visible to near infrared. CL observation has shown that point defects diffused out from implanted region to ~10 µm depth during activation annealing. Annealing temperature dependence of the depth distribution of CL intensity of these defects has suggested that structural transformation of point defects proceeds as “silicon vacancy (VSi) → carbon vacancy-antisite pair (VC-CSi ; UD2) → antisite pair (CSi-SiC ; DI)”.

Abstract: We have studied InGaN single-quantum-well (SQW) films using atomic force microscopy (AFM) and cathodoluminescence (CL) spectroscopy. It has been found that a screw dislocations (SDs) distribution in the height image by AFM is well correlated with images of the CL spectra at about 440nm assigned to the spontaneous emission from the InGaN SQW. These results at least mean an existence of non-radiative recombination centers within the InGaN SQW films. It has been also found that the average period of the peak-intensity and the FWHM change is smaller than that of the peak-wavelength change assigned to InN mole fluctuations. These results suggest that the exciton diffusion length of the spontaneous emission at about 440nm is not larger than the average period of InN mole fluctuations in the InGaN SQW.

Abstract: Cross-sectional CL measurements have been performed on the cleaved surface of the Al-ion implanted 4H-SiC. The strong L1 luminescence that originates from the DI defect has been observed even in the deep region (~10 μm) where implanted ions do not penetrate. In the implanted layer, CL results show that high-density non-radiative defects remain even after activation annealing. Generation of the DI defect in the deep region is presumably attributed to the diffusion of point defects from the implanted layer.