Quantum efficiency and formation of the emission line in light-emitting diodes based on InGaN/GaN quantum well structures
Quantum efficiency and formation of the emission line in light-emitting diodes based on InGaN/GaN quantum well structures
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基于InGaN/GaN量子阱结构的发光二极管的量子效率和发射线的形成
DOI：
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发表时间：
2007
期刊：
影响因子：
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通讯作者：
Y. Shreter
中科院分区：
文献类型：
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作者：
N. Bochkareva;D. V. Tarkhin;Y. Rebane;R. Gorbunov;Y. Lelikov;I. Martynov;Y. Shreter
研究了In0.2Ga0.8N/GaN量子阱结构的电致发光、光致发光和光电流谱，阐明了量子效率随正向电流增加而降低的原因。结果表明，在In0.2Ga0.8N层中，随着发射光子能量接近迁移率边缘，量子效率降低。由光电流谱确定的迁移率边为Eme=2.89 eV。在光子能量为hv>；2.69 eV时，载流子能以一定的概率隧穿到非辐射复合中心，从而使量子效率降低。隧道注入到深局域态提供了最大的电致发光效率。这一效应是导致电流密度远低于工作密度时发光二极管量子效率出现特征极大值的原因。在InGaN的态密度“尾部”中，深局域态的占据对发射线的形成也起着至关重要的作用。结果表明，量子效率的提高和光致发光光谱随电压的“红移”与光电流的变化有关，这是由于光生载流子在空间电荷场中的分离被抑制以及它们被热化到深局域态所致。
The spectra of electroluminescence, photoluminescence, and photocurrent for the In0.2Ga0.8N/GaN quantum-well structures are studied to clarify the causes for the reduction in quantum efficiency with increasing forward current. It is established that the quantum efficiency decreases as the emitting photon energy approaches the mobility edge in the In0.2Ga0.8N layer. The mobility edge determined from the photocurrent spectra is Eme = 2.89 eV. At the photon energies hv > 2.69 eV, the charge carriers can tunnel to nonradiative recombination centers with a certain probability, and therefore, the quantum efficiency decreases. The tunnel injection into deep localized states provides the maximum electroluminescence efficiency. This effect is responsible for the origin of the characteristic maximum in the quantum efficiency of the emitting diodes at current densities much lower than the operating densities. Occupation of the deep localized states in the density-of-states “tails” in InGaN plays a crucial role in the formation of the emission line as well. It is shown that the increase in the quantum efficiency and the “red” shift of the photoluminescence spectra with the voltage correlate with the changes in the photocurrent and occur due to suppression of the separation of photogenerated carriers in the field of the space charge region and to their thermalization to deep local states.