Preliminary Analysis Of Nonlinear Characteristics Of Photocarrier Radiometry Methods

The semiconductor material represented by silicon crystal is the basic material of the electronic device and the photovoltaic device,and the performance of devices are affected by the inpurity and defect properties of the materials.Therefore it is crucial to develop the detection methods of semiconductor electrical characteristics parameters,carrier transport parameters characterizing the inpurity and defect of the material.Nowadays,optical and non-destructive measurements for the semiconductor material parameters are the hot spots and trends.Photocarrier Radiometry(PCR),a all-optical,non-destructive and dynamically modulated detective means is used to detect the carrier transport parameters including lifetime,diffusivity,and surface recombination velocities.It is indicated by experimental results that it is non-linear between the PCR signal and the excitation light intensity.But this phenomena was not considered in the traditional PCR theory model.Therefore,the preliminary analysis for the affection of PCR signal of nonlinear characteristics on detection of carrier transport parameters are the primary contents in this article.This article is started through the physical mechanism of the PCR signal nonlinear characteristics.The concepts of carrier generation,recombination and transportion are introduced to make the carrier motion behavior understood and the expression of the carrier radiation signal is also presented through seeking the carrier transport equation.From the theory of spontaneous emission of radiation the relationship of between PCR signal and the carrier concentration and the doping concentration of semiconductor samples is presented and the nonlinear coefficient of PCR intensity response is also expounded.The theoretical simulation is presented through the theoretical relation of the PCR signal and the affects of the relative parameters on the PCR signal are simulated,including the carrier transport parameters and the PCR intensity response nonlinear coefficient.The applicable conditions of the nonlinear model and the traditional linear model are also given,and the affect of PCR nonlinear model on the detection of the carrier transport parameters is described in this part.An optical experimental platform through transmitted light monitoring the intensity of the excitation light is built.The experiments PCR frequency sweeping and PCR intensity sweeping are carried out.The application of nonlinear model and traditional linear model is verified experimentally by analyzing the PCR intensity response nonlinear effects of different processes and different resistivity samples,and inverting carrier transport parameters.The PCR intensity response and frequency response of different resistivity samples are measured,selecting the appropriate fitting model,obtaining carrier transport parameters.