Blueshifts of the emission energy in type-II quantum dot and quantum ring nanostructures
Blueshifts of the emission energy in type-II quantum dot and quantum ring nanostructures
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DOI：
10.1063/1.4818834
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发表时间：
2013-08
影响因子：
3.2
通讯作者：
P. Hodgson;R. Young;M. A. Kamarudin;P. Carrington;A. Krier;Q. Zhuang;Ep Erwin Smakman;P. Koenraad;M. Hayne
中科院分区：
文献类型：
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作者：
P. Hodgson;R. Young;M. A. Kamarudin;P. Carrington;A. Krier;Q. Zhuang;Ep Erwin Smakman;P. Koenraad;M. Hayne
研究了11个GaSb/GaAs量子点/环（QD/QR）样品在大于等于5个数量级的激光功率下的系综光致发光（PL）。所有样品表现出PL能量的蓝移，Δ E，随着激发功率的增加，如II型结构所预期的。通常认为这种蓝移是由于II型界面处的能带弯曲。然而，对于样品中观察到的PL发射内的电荷状态的子峰，它是明确地表明，由于电容充电的蓝移是一个数量级大于能带弯曲的贡献。此外，蓝移的大小和它的线性依赖于通过一个简单的电容模型预测的占用忠实地复制在数据中。相反，当QD/QR发射强度I用于通过双分子复合近似（I α n（2））推断QD/QR占有率n时，Δ E α I-x中的指数x始终低于预期，并且强烈依赖于样品。我们的结论是，指数x不能用来区分电容充电和能带弯曲的起源，在II型QD/QRs的蓝移，因为双分子复合是不适用于II型QD/QRs。(C)2013 AIP Publishing LLC.
We have studied the ensemble photoluminescence (PL) of 11 GaSb/GaAs quantum dot/ring (QD/QR) samples over >= 5 orders of magnitude of laser power. All samples exhibit a blueshift of PL energy, Delta E, with increasing excitation power, as expected for type-II structures. It is often assumed that this blueshift is due to band-bending at the type-II interface. However, for a sample where charge-state sub-peaks are observed within the PL emission, it is unequivocally shown that the blueshift due to capacitive charging is an order of magnitude larger than the band bending contribution. Moreover, the size of the blueshift and its linear dependence on occupancy predicted by a simple capacitive model are faithfully replicated in the data. In contrast, when QD/QR emission intensity, I, is used to infer QD/QR occupancy, n, via the bimolecular recombination approximation (I alpha n(2)), exponents, x, in Delta E alpha I-x are consistently lower than expected, and strongly sample dependent. We conclude that the exponent x cannot be used to differentiate between capacitive charging and band bending as the origin of the blueshift in type-II QD/QRs, because the bimolecular recombination is not applicable to type-II QD/QRs. (C) 2013 AIP Publishing LLC.