期刊
ACS PHOTONICS
卷 5, 期 3, 页码 820-826出版社
AMER CHEMICAL SOC
DOI: 10.1021/acsphotonics.7b00944
关键词
InGaN; efficiency droop; light-emitting diode; carrier dynamics; time-resolved spectroscopy
类别
资金
- King Abdullah University of Science and Technology
We investigate the effects of V-pits on the optical properties of a state-of-the-art, highly efficient, blue InGaN/GaN multi-quantum-well (MQW) light-emitting diode (LED) with a high internal quantum efficiency (IQE) of > 80%. The LED is structurally enhanced by incorporating a pre-MQW InGaN strain-relief layer with low InN content and a patterned sapphire substrate. For comparison, a conventional (unenhanced) InGaN/GaN MQW LED (with an IQE of 46%) grown under similar conditions was subjected to the same measurements. Scanning transmission electron microscopy reveals the absence of V-pits in the unenhanced LED, whereas in the enhanced LED, V-pits with {10-11} facets, emerging from threading dislocations (TDs), were prominent. Cathodoluminescence mapping reveals the luminescence properties near the V-pits, showing that the formation of V-pit defects can encourage the growth of defect-neutralizing barriers around TD defect states. The diminished contribution of TDs in the MQWs allows indium-rich localization sites to act as efficient recombination centers. Photoluminescence and time-resolved spectroscopy measurements suggest that the V-pits play a significant role in the generated carrier rate and droop mechanism, showing that the quantum-confined Stark effect is suppressed at low generated carrier density, after which the carrier dynamics and droop are governed by the carrier overflow effect.
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