Mapping the charge carrier density in semiconductors by THz-QCL based optical feedback interferometry

摘要

A THz imaging system based on self-mixing (SM) interferometry in a Quantum Cascade Laser (QCL) is developed to map the distribution of free charges on a semiconductor surface. In the experiment, a free electron plasma is photo-generated in a high resistivity n-type silicon wafer using a near-infrared (NIR) continuous-wave (CW) pump laser. A model based on Drude theory correctly reproduces the experimental results and in prospective promises a quantitative evaluation of the free charges density.