Prototype Fabrication Research of Ultra-sensitive Optical Sensor Using Charging Effect of Quantum Dots

我们用电子隧道谱和电导谱研究了InAs自组装点的电子态。这两种类型的测量都是基于内置的器件结构进行的，这些结构是与自组装量子点一起特别设计的。这两种方法在研究自组装InAs点中的电子态方面起着至关重要的作用，因为不同于通常的光学方法，如光致发光测量，可以直接监测电子态。主要成果如下。(I)为了阐明基于充电效应的高分辨率传感器中的点尺寸变化对传感器性能的影响，我们验证了电子态(类1s态、类1p态、类1d态、类2s态)及其与磁场的关系，并用目前的电子隧穿方法很好地解决了这些变化。通过对反磁SHI…的观测，估计了点内的平均波函数范围更多的FTS和结果很好地解释了基于AFM测量估计的网点大小的估计。隧道光谱结果与本项目成员之一平川教授的远红外吸收实验结果一致。(Ii)为了克服量子点的尺寸变化效应，我们提出并研究了一种新的器件结构，该结构在一个器件中包含几千个点，并通过沟道电导测量平均的单点状态。除了避免光点尺寸变化的特点外，目前的器件结构还具有增加小散射截面的优点，这是利用电荷效应的超灵敏光学传感器的主要缺点。经验证，该装置具有足够高的灵敏度，可以监测平均“单点”的电子充电状态。这是使用异质结晶体管结构的内置电导方法观察壳层结构的第一个演示。较少

We have investigated the electronic states of self-assembled InAs dots through electron tunneling spectroscopy and conductance spectroscopy. Both types of measurements were performed based on the built-in device structures which were specially designed together with the self-assembled quantum dots. Both methods plays crutial role to investigate electronic states in the self assembled InAs dots because electron states can be directly monitored unlike commonly performed optical methods such as the photoluminescence measurements. Major results are listed as follows. (I) In order to clarify the effects of dot size variations on the performance of high resolution sensors based on charging effects, we have verified electronic states (1s-like, 1p-like, 1d-like, 2s-like states) and their magnetic fields dependence and that the variations were well resolved by the present electron tunneling method. The average wave function extent in the dots were estimated by the observation of diamagnetic shi … More fts and the results were well accounted for by the estimation based on the dot size estimated by the AFM measurements. The tunneling spectroscopy results were found to be consistent with the far-infrared absorption experiment which were performed by Professor Hirakawa who is one of the member investigators of the present projects. (ii) In order to overcome the size variation effects of the quantum dots, we have proposed and investigated the new device structure which contains several thousands of dots in one device and measures averaged "single dot" states through channel conductance. In addition to the the feature of aviding the dot size variation, the present device structure has also an advantage of increasing the small scattering cross-sections which is the major weakness of the ultra-sensitive optical sensors using charging effects. The present device was verified to be sensitive enough to monitor the electron charging states of an average "single dot". This was the first demonstration to observe shell structures by the built-in conductance methods using heterojunction transistor structures. Less