考虑应变对量子点结构产生的重要影响,采用六带K·P理论模型计算了耦合量子点系统在不同耦合距离下空穴基态及激发态的能态特性,探讨了应变效应对耦合量子点空穴基态反成键态特性的影响。计算结果表明,单轴应变对量子点的空穴能带有主要影响:首先它使重空穴(HH),轻空穴(LH)能级分裂增加,减少了HH,LH的混合;同时,改变了LH的束缚势垒,使得空穴基态波函数较多局限在底部量子点中。在不考虑应变的情况下,随着量子点之间耦合强度的减小,价带基态能级和激发态能级发生反交叉现象,基态从成键态翻转为反成键态。应变效应使得量子点的重空穴及轻空穴的能带发生改变,轻重空穴耦合减弱,基态和激发态之间发生成键、反成键态翻转的临界距离明显减小。
In consideration of the effect of consequent elastic strain due to the lattice mismatch on the electronic structures of Quantum Dots( QDs), a six-band K ~ P model was used to explore the two lowest single-particle hole states in two vertically Coupled InAs/GaAs QDs (CQDs). The elastic strain due to the lattice mismatch between InAs and GaAs was included in the calculations. The theo- retical results indicate that uniaxial strain effects play a dominant role in the band offset and they af- fect the hole states of the coupled dot system. First, it increases the splitting energy between the heavy-hole (HH) and light-hole (LH) levels and reduces the mixing of HH and LH. Simultaneously, the strain in the dot molecule affects the potential distribution of CQDs, inducing more ground states are confined on the bottom dots. Compared to the case without strain effect, the critical distance be- tween QDs is reduced to about 2 nm, by which the hole ground states are anti-bonding-like. There- fore, the strain effects in the CQDs change the potential distribution,weaken the coupling strength be- tween HH and LH and reduce the critical inter-dot distance.