Spatially Resolved Spectroscopy of Blue and Green InGaN Quantum Wells by Scanning Near‐Field Optical Microscopy
PHYSICA STATUS SOLIDI B-BASIC SOLID STATE PHYSICS(2018)
摘要
We investigated nanoscopic spectroscopy of blue and green InGaN multiple quantum wells (MQWs) by scanning near-field optical microscopy (SNOM). The photoluminescence (PL) spectra showed emission peaks related to GaN and a main InGaN peak both in the blue and green MQWs. In addition, local emission peaks appeared on the higher-energy side of the main InGaN peak (high-E emission) in only the green InGaN MQW. The PL intensity map acquired from the high-E emission in the green MQW was compared with the GaN emission intensity map, and there was no clear correlation between the high-E emission regions and the dark spots in the GaN emission intensity map at room temperature (RT). The high-E emissions are not due to potential barriers, but to other defects in the quantum wells. This may be because there is no high-E emission related to the potential barrier at RT owing to the small V-pit size, which reduces the suppression of carrier diffusion into dislocations especially at RT. Thus, the SNOM-PL is measured for the green MQW at low temperature. In contrast to RT, there was a clear correlation between the high-E emission regions and the dark spots in the GaN emission intensity map at 40K, indicating that potential barriers formed around threading dislocations. The potential barrier height estimated from the SNOM-PL spectra of the green MQW was sufficient to suppress carrier diffusion into threading dislocations.
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关键词
III-nitride semiconductors,InGaN,quantum wells,scanning near-field optical microscopy,spatially resolved spectroscopy
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