InGaN/GaN quantum wells (QWs) grown at identical conditions on m-plane GaN and c-plane sapphire substrates were characterized by several techniques, aiming to clarify the reason for different emission wavelengths often observed in similar LED structures with m-and c-plane surface orientations. Cathodoluminescence (CL) spectra of m-plane QWs revealed shorter wavelength and no blueshift with increasing CL probe current in accordance with previous reports. Relative indium compositions were estimated by high-resolution X-ray diffrac-tion to be 5.1 and 13.9% for m-plane and c-plane QWs, respectively. Cross-sectional transmission electron microscopy images revealed that the well widths of the m-plane QWs were noticeably thicker than those of the c-plane QWs. The lower indium compositions and thicker well widths of the m-plane QWs indicated that different indium incorporation and diffusion occurred in the structures grown on the GaN substrate, which is attributed to its surface off-cut toward [0001] and the higher thermal conductivity with respect to that of sapphire.
InGaN/GaN quantum wells (QWs) grown with identical conditions on m-plane and c-plane GaN substrates were studied by cathodoluminescence spectroscopy. At a low current of 10 nA, the emission intensity and wavelength of the m-plane aligned QWs were found to be about two times stronger and 19.5 nm blueshifted with respect to that of the c-plane aligned QWs. An increase in the current over three orders of magnitude was found to result in an increase in the emission intensities, with faster saturation in the m-plane aligned QWs. This was explained by the screening of quantum-confined Stark effect in the emission efficiency of the c-plane aligned QWs.
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