论文标题
用飞秒激光激发的半导体表面产生Terahertz波的简化公式
Simplified formulas for the generation of terahertz waves from semiconductor surfaces excited with a femtosecond laser
论文作者
论文摘要
我们得出简单的公式来解释由飞秒（FS）激光激发的半导体表面的Terahertz（THz）发射。根据光电流的时间导数，具有大于带隙的能量的飞秒光学脉冲会产生传播和产生Thz辐射的光载体。通过假设只有不到几百fs的超快时间尺度传播的电子会导致THZ辐射，就可以从源自光载体漂移的光载体漂移或使用光载体扩散加速的发射器上获得简单的表达式。前者的发射幅度与电子迁移率，肖特基凸线高度以及激光强度以及后者之一的激光强度和扩散系数平方成比例。我们还讨论了金属 - 绝缘子 - 轴向导体结构排放的公式。派生的表达式有助于理解激光THZ发射显微镜（LTEM）观察到的THZ发射特性，从而使LTEM进入了半导体研究和开发领域的实际应用。
We derive simple formulas to explain terahertz (THz) emission from semiconductor surfaces excited by a femtosecond (fs) laser. Femtosecond optical pulses with energies larger than the bandgap create photocarriers which travel and generate THz radiation, according to the time derivative of the photocurrent. By assuming that only electrons traveling in an ultrafast time scale, less than a few hundred fs, contribute to THz radiation, one can obtain simple expressions for the emission originating from the photocarrier drift accelerated with a built-in field or from the photocarrier diffusion. The emission amplitude of the former is in proportion with electron mobility, the Schottky-Barrier height, and the laser intensity and one of the latter with the laser intensity and diffusion coefficient squared. We also discuss the formula for emission from metal-insulator-semiconductor structures. The derived expressions are useful in understanding the THz emission properties observed by a laser THz emission microscope (LTEM), bringing LTEM into real applications in the field of semiconductor research and development.
