Electron-electron Interaction and Dynamic of Electrons in a Vertically Aligned Double Dot System

1)利用GaAs/AlGaAs异质结构制备了垂直排列的双点结构，并在远红外（FIR）磁光吸收测量中观察到两个点上的电子有两个共振峰。在AlGaAs层的脉冲带隙光激发下，两个峰根据激发强度和延迟时间向更高的磁场偏移。通过计算机模拟，我们证实了峰移包含了垂直排列的双点系统的点间耦合信息。2)为了定量研究点间耦合，我们利用超短脉冲激光制作了时间分辨光致发光（PL）测量系统和时间分辨光探测回旋共振测量系统。通过测量系统，我们研究了GaAs/AlGaAs异质结构中二维电子气体（2DEG）的发射峰（称为h波段发射）。结果表明，发射与激发光的波长密切相关。在这次测量中，我们用Ar+激光照射样品，同时用探测Ti：蓝宝石激光照射样品。前者激发了AlGaAs层中的电子空穴对，并改变了限制2DEG的势分布。在时间分辨PL测量中，我们有直接证据表明AlGaAs层中产生的空穴向GaAs层流动并与2DEG重新结合。3)在FIR吸收测量中，我们发现了InGaAs/InAlAs异质结构中电子的零场自旋分裂，可以估计样品的自旋分裂能Δ_R为9 meV。我们可以证明FIR吸收测量对于估算Δ_R是非常有用的技术。我们还展示了带隙光照射对Δ_R值的调整，这改变了约束势的分布。

1) We fabricated vertically aligned double dot structures using GaAs/AlGaAs heterostructures and observed two resonance peaks of electrons in both two dots in a far-infrared (FIR) magneto-optical absorption measurements. Under photoexcitation with pulsed bandgap light of AlGaAs layer, the two peaks are shifted toward higher magnetic filed, depending on excitation intensity and delay time. From computer simulations, we confirmed that the peak shift includes information on an interdot coupling of the vertically aligned double dot system.2) For the quantitative investigation of the interdot coupling, we made time resolved photoluminescence (PL) measurement system and time resolved optically detected cyclotron resonance measurement system with ultrashort pulse laser. By using the measuring systems, we investigated emission peak (called as H-band emission) due to 2 dimensional electron gas (2DEG) in GaAs/AlGaAs heterostructures which is a starting material of our dot system. It is confirmed that the emission strongly depend on the wavelength of the excitation light. In this measurement, we illuminated the sample with Ar+ laser, as well as the illumination of the probing Ti:sapphire laser. The former excites electron-hole pairs in AlGaAs layer and is found to change the potential profile confining 2DEG. We have direct evidence the generated holes in AlGaAs layer flow toward GaAs layer and recombine with 2DEG in the time resolved PL measurements.3) In FIR absorption measurement, we found the zero-field spin splitting of electrons in InGaAs/InAlAs heterostructures and could estimate the value of spin-splitting energy Δ_R of a sample as 9 meV. We could show the FIR absorption measurement is quite useful technique for the estimation of Δ_R. We also show the tuning of the value of Δ_R by the bandgap light illumination which changes the confinement potential profile.