MBE生长的垂直堆垛InAs量子点及HFET存储器件的应用

Vertically Stacked, Self-assembled MBE-grown InAs Quantum Dots and Application of Field Effect Transistor

用MBE设备以Stranski Krastanov生长方式外延生长了5个周期垂直堆垛的InAs量子点,在生长过程中通过对量子点形状、尺寸的控制来提高垂直堆垛InAs量子点质量和均匀性。用原子力显微镜(AFM)进行表面形貌的表征,并利用光致发光(PL)和深能级瞬态谱(DLTS)对InAs量子点进行观测。所用Al0 5Ga0 5As势垒外延层,对镶嵌在其中的InAs量子点有很强的量子限制作用,并产生强量子限制效应,可以把InAs量子点的电子和空穴能级的热激发当作"深能级"的热激发来研究,这样可用DLTS方法进行测量。在垂直堆垛的InAs量子点的HFET器件中,由充电和放电过程的IDS VGS曲线可以看到阈值电压有非常大的移动,这样便产生存储效应。

The epilayer of vertically stacked, selfassembled InAs Quantum Dots (QDs) was grown by MBE with solid sources in noncracking Kcells, and the sample was fabricated to a FET structure using a conventional technology. A quantum dot (QD), the behavior of which is to capture and emit carriers like a giant trap, is studied using deep level transient spectroscopy (DLTS) technique. The electrons and holes in the QDs are respectively emitted from the relevant energy levels to the conduction and valence bands of the barrier layer with increasing measurement temperature, and the thermal emission energies from the QDs are related to their discrete energy levels. The 5period vertically stacked InAs QDs in the barrier layer of a fieldeffect type structure were measured, and the results were found to correspond to the capacitancevoltage and photoluminescence properties. At 77K and room temperature, the threshold voltage shift values are 075V and 035V, which are caused by the trapping and detrapping of electrons in the quantum dots. Discharging and charging curves form a part of a hysteresis loop exhibiting a memory function. The electrical injection of confined electrons in QDs products the threshold voltage shift and memory function with the persistent electron trapping, which shows the potential use for a room temperature application.