New Optoelectronic Technique for Characterization of Semiconductors

9307419张这项研究计划的目标是开发一种用于表征半导体的新的光电子技术。这项新技术提供了对表面和界面的电子性质以及载流子动力学(相位和幅度)的相干测量。该技术包括使用飞秒激光照射半导体，并测量由于自由载流子光学注入半导体中的静电场和磁场而产生的快速电流瞬变所产生的电磁辐射。通过测量辐射电场的时域波形，可以用非接触的方法确定静电场的强度和方向。一个直接的应用是研究生长样品上半导体表面和界面的静电场的形成动力学。可以直接监测界面场(场向和场强)对半导体的影响。在单层外延生长、表面电化学钝化、超薄金属层沉积以及样品从液氦温度到熔化温度的过程中。我们将详细阐述与界面场相关的虚拟载流子布居和强磁场下的载流子输运(皮秒量子霍尔效应)等现象。***

9307419 Zhang The objective of this research plan is to develop a new optoelectronic technique for the characterization of semiconductors. The new technique offers coherent measurement of the electronic properties of surfaces and interfaces, as well as carrier dynamics (both phase and amplitude). The technique consists of using a femtosecond laser to illuminate semiconductors, and measuring the electromagnetic radiation produced by the rapid current transients due to optical injection of free carriers into static electric and magnetic fields in the semiconductors. By measuring the time domain waveform of the radiated electric field, the strength and direction of the static electric field can be determined with a non contact approach. A direct application is studying the formation dynamics of the static fields of semiconductor surfaces and interfaces on as grown samples. The influence of the interface fields (both field direction and strength) on the semiconductor can be monitored directly. During monolayer epitaxial growth, surface electrochemical passivation, ultrathin metallic layer deposition, as well as when the sample goes from the liquid helium temperature to its melting temperature. Phenomena such as virtual carrier population associated with the interface field and carrier transport (picosecond quantum Hall effect) at high magnetic fields will be elaborated upon. ***