Control of Optical Properties of Quantum Well Structures by Carrier Induced Effects and its Applications to Novel Optical Devices

1.势插入量子威尔斯阱中光场诱导吸收边蓝移的证明为了在量子威尔斯阱中获得一种新颖的电光效应，我们提出了一种势插入量子阱（PI-QW），它是在两个相互耦合的威尔斯阱之间用薄的AlAs势垒隔开。PI-QW表现出独特的场致光学效应，因为电子和空穴之间的重叠矩阵元比常规QW更强地被横向电场F调制。我们观察到了F作用下吸收边的蓝移，它与通常量子阱中的Stark位移方向相反，证明了PI-QW的一个独特特性。2.量子阱结构中载流子诱导光学效应的控制和澄清为了澄清载流子诱导光学效应，我们研究了量子阱场效应晶体管（QW-FET）的光学特性。随着电子密度的增加，吸收边向高能方向移动，发光峰向低能方向移动。 ...更多信息 通过与理论的比较，定量地解释了带填充效应和多体效应。此外，我们已经表明，这种载流子诱导的漂白和伴随的折射率变化可以应用于光调制器和开关。3载流子诱导的二维激子态的不稳定性和高磁场下激子相互作用的增强为了揭示复合过程是激子还是自由载流子，研究了不同电子浓度下量子阱场效应晶体管（QW-FET）光致发光的磁场依赖性。论证了载流子诱导复合过程从激子主导到自由载流子主导的转变。此外，还研究了强磁场对量子阱中自由载流子复合的影响，结果表明，在强磁场下，量子阱中的自由载流子复合过程恢复了激子特性。4共振隧穿结构中的载流子诱导光学效应在双势垒共振隧穿二极管（DBRTD）中，电子在共振条件下聚集在DBRTD的QW区。因此，人们期望在DBRTD中的载流子诱导光学效应。在共振条件下，我们清楚地观察到吸收边的蓝移和光致发光能量的降低，并由此确定了累积电子浓度。吸收光谱的蓝移表明了DBRTD在高速光调制器和光开关中的应用。少

1. Demonstration of the field-induced blue-shift of the absorption edge in potential inserted quantum wells To get a novel electro-optic effect in quantum wells(QW), we proposed a potential inserted QWS(PI-QW), in which two coupled wells are separated by a thin AlAs barrier. PI-QWs are exhibit a unique field- induced optical effect since the overlap matrix elements between electrons and holes are more strongly modulated by the transverse electric fields F than in conventional QWs. We have observed the blue shift of the absorption edge by applying F , which is opposite in direction to the Stark shift in usual QWs, demonstrating a unique feature of PI-QWs.2.Control and clarification of carrier induced optical effect in QW structures To clarify carrier induced optical effects, we have investigated optical properties of QW field effect transistors(QW-FET). With the increase of electron density, the absorption edge shifted to higher energy and the luminescence peak shifted to lower energy. … More By comparing these observations with theory, the bandfilling and many body effect are quantitatively clarified. Furthermore, we have shown that this carrier induced bleaching and the accompanied change of refractive index can be applied to optical modulators and switches.3 Carrier-induced instability of two dimensional excitonic state and enhancement of excitonic interaction under high magnetic fields To disclose whether the recombination process is excitonic or free carrier like, the magnetic field dependence of photoluminescence is studied in QW-FETs at various electron concentration. The carrier induced transition of recombination process from excitonic to free carrier dominated process is demonstrated. In addition, the effect of high magnetic fields on free carrier recombination is studied to show that excitonic feature is recovered in recombination processes in QWs at. high magnetic fields, demonstrating the formation of magneto exciton.4 Carrier-induced optical effect in resonant tunneling structure In double barrier resonant tunneling diode(DBRTD), electrons are accumulated in the QW region of DBRTD under the resonant condition. Thus, one expects the carrier induced optical effect in DBRTD. We have observed clearly the blue shift of the absorption edge and lowering of photoluminescence energy under the resonant condition, from which the accumulated electron concentration is determined. The observed blue shift of absorption suggests the applicability of DBRTD to high speed optical modulators and switches. Less