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

我们利用电子隧穿光谱和电导光谱研究了自组装的InAs点的电子态。这两种测量都是基于专门设计的内置器件结构与自组装量子点一起进行的。这两种方法对于研究自组装InAs点中的电子态都起着至关重要的作用，因为电子态可以直接监测，而不像通常的光学方法（如光致发光测量）。主要结果如下：(1)为了阐明点尺寸变化对基于电荷效应的高分辨率传感器性能的影响，我们验证了电子态（1s-like, 1p-like, 1d-like, 2s-like）及其对磁场的依赖关系，并通过本电子隧穿方法很好地解决了这些变化。根据原子力显微镜测量得到的点的大小，估计出了点的平均波函数范围。隧道光谱结果与本项目研究人员之一平川教授所做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，我们提出并研究了在一个器件中包含数千个量子点的新器件结构，并通过通道电导测量平均“单点”状态。除了避免了网点尺寸变化的特点外，该器件结构还具有增加小散射截面的优点，而小散射截面是利用充电效应的超灵敏光学传感器的主要弱点。该装置被证实具有足够的灵敏度，可以监测平均“单点”的电子充电状态。这是首次利用异质结晶体管结构用内置电导法观察壳层结构。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