Infrared-detector and FET applications and velocity modulation effect using hetero-coupling

我们考虑由两个耦合的量子结构组成的器件。人们可以通过控制两者之间的电或光耦合强度来极大地改变这类器件的物理性质。这为我们制造具有标准单量子结构器件所不能实现的独特功能的新型器件提供了可能性。因此，我们研究了以下现象，以探讨利用速度调制效应或红外探测器制作FET的可能性。(1)我们设计并制作了一种由双量子阱组成的FET，其中只有一个量子阱掺杂了施主。在该器件中，在正常工作条件下，限制在高迁移率沟道中的电子主导着器件的输运特性。然而，通过调整栅极电压，使得两个量子阱处于共振状态，所有的电子都会受到杂质的影响，迁移率将显著提高。…降幅更小一些。在这种情况下，我们观察到了负互导。(2)我们设计并制作了一种由自组装的InAs量子点埋入沟道和栅间的反向HEMT结构的FET结构，其中以GaAs层和n-AlGaAs层的界面作为传输通道。利用这种器件，我们观察到，通过控制栅电场，沟道中的电子可以被捕获到量子点中，从而表现出速度调制或作为存储器件的功能。(3)我们通过在相邻的由大约20 nm的多原子台阶组成的GaAs(111)衬底上生长n-AlGaAs来制备FET。利用该装置，我们研究了控制台阶界面电子散射的可能性。(4)在由两个量子阱组成的结构中，光生电子和电场作用下的空穴在不同的势垒中弛豫。通过共振激发电子到具有激发态的激发态，我们观察到了带间发光，因为电子可以在势垒之间来回移动。较少

We consider devices that consist of two coupled quantum structures. One can vary drastically the physical properties of such devices by controlling the strength of coupling between the two either electrically or optically. This opens up a possibility for us to fabricate novel devices with unique features that could not have been realized by standard single quantum structure devices. We have therefore studied the following phenomena in order to discuss the possibility of producing FETs using the velocity modulation effect or infrared detectors.(1) We have designed and fabricated an FET that consists of double quantum wells, only one of which is doped with donors. In this device, under normal operational conditions, the electrons confined in the channel with high mobility dominate the transport property of the device. However, by adjusting the gate voltage so that the two quantum wells are in resonance, all electrons will be influenced by the impurities and the mobility will be significa … More ntly reduced. Under such a condition, we observed a negative mutual-conductance.(2) We have designed and fabricated an FET structure that consists of self-assembled InAs quantum dots buried in between channel and gate in an reverse HEMT structure of which the interface of GaAs and n-AlGaAs layrs acts as the transport channel. With this device, we observed that electrons in the channel can be trapped into the quantum dots by controlling the gate electric field, and as a result exhibit velocity modulation or function as a memory device.(3) We have fabricated an FET by growing n-AlGaAs on a vicinal GaAs (111) substrate that consists of multi-atomic steps at an interval of about 20nm. With this device we have investigated the possiblity of controlling electron scattering that occur at step interfaces.(4) In a structure that consists of two quantum wells, photo-generated electrons and holes under electric field relax into diffrent wells. By excitating electrons to the excited states with excitated states in resonance, we observed inter-band luminescence since the electrons can move back and forth between the wells. Less