Extremely weak surface emission from (0001) c-plane AlGaN multiple quantum well structure in deep-ultraviolet spectral region

We studied the anisotropic optical properties of c-plane AlxGa1−xN multiple quantum wells and m-plane AlxGa1−xN single layer grown on a SiC substrate. Very weak surface emission was detected from c-plane samples with x=0.66–0.76 (emission wavelength of 228–240nm), although strong surface emission was detected from c-plane samples with x=0–0.41 (280–365nm) and m-plane samples with x=0–0.76 (240–365nm). These results indicate that crystal-field splitoff hole valence band plays an important role in (E‖c) polarization and isotropic emissions from AlxGa1−xN with x≧0.5.