Laser terahertz emission microscopy for silicon electronics

Terahertz (THz) emission from the silicon (Si) surface by the femtosecond laser illumination shows a lot of information, known as the THz emission spectroscopy (TES) or the laser-induced THz emission microscope (LTEM), which seems to be the promising method for evaluating the surface/interface properties of Si-based devices, such as Si metal-oxide-semiconductor (Si MOS) structure. To enlarge the application and explore silicon electronics, it is necessary to build a theoretical model, which can accurately and simply describe the relationship between the THz emission amplitude and the external bias voltage on the Si MOS structure. Here, we focus on the THz emission spectrum from the p-type Si MOS structure and discuss the THz emission field under different DC bias conditions. The theoretical model is derived from Poisson's equation and shows great consistency with the experiment results. Besides that, the flat-band voltage, interface trap states, and photo-Dember effect have been discussed to modify the model.