Abstract
A new photoluminescence (PL) microscope has been developed with a conventional optical system to obtain a monochromated PL image at a low temperature with a spatial resolution in sub-micron range. The objective and sample were put in the identical vacuum chamber to ensure thermal insulation between them. The spatial resolution at 15K was confirmed to be almost equal to the diffraction limit, i.e., 0.3μm, at a wavelength of 488nm. The microscope clearly visualized defective region, and polytype domain with a spatial resolution of 0.3μm in GaN. PL emissions ascribed to free excitons (EXA) and excitons bound to donors (D0X) were discriminated in μ-PL measurements at 15K on epitaxially laterally overgrown (ELO) GaN. The emission at 3.487eV ascribed to D0X became strong above the SiO2 mask within a distance of 8μm from the mask. In a μ-PL image related to excitons bound to N atoms in a 4H-SiC homoepitaxial layer, a dark line was observed at a line-shaped surface defect. Since the PL emission from donor (N)-acceptor (B) pairs was spatially uniform, N atoms were incorporated uniformly in the 4H-SiC epilayer. The dark line is probably caused by an enhancement of nonradiative recombination at the surface defect.
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