Mechanisms Of Photothermal Effects In Semiconductor With The Step Optical Exciation

In recent years, due to the rapid development of the microelectronic industry, people are paying more and more attention to semiconductor which is one of the most important materials in electronics industry. The measurement of semiconductor material properties needs highly sensitive and high resolution testing method. Photoacoustic and photothermal technique is widely used in scientific research and industry application because of its high sensitivity, widespread applicability, nondestructive and non-contact measurement. Traditional photoacoustic and photothermal technique research mainly focus on the analysis of signal amplitude and phase. The measurement devices usually use modulation light or pulse light as excitation light source and the experimental apparatus are relatively complex. The signal acquisition also needs subsequent processing. In order to make the application more widely used and more simple, the opinion that using step light as excitation source is put forward. This thesis describes briefly the application and development of photoacoustic and photothermal technique in semiconductor measurements. The theoretical and experiment research of semiconductor photothermal deflection and reflection with step optical excitation are performed in this thesis as follows:1.On the basis of taking step light as excitation source, theoretical studies of photothermal deflection technique with step optical excitation are performed systematically. According to and heat conduction theory of solid and gas, a three-dimensional photothermal model of semiconductor materials with step optical excitation is established and solved using the Green function method. The characteristics of temperature field of air above the sample surface changing with time are numerical simulated. The influences of experiment conditions and material parameters on deflection signal are also studied.2. A three-dimensional model of photothermal reflectance of semiconductor materials with the step optical excitation is established. The temperature variation in semiconductor is solved by using the eigen-function. Photogenerated carrier density in semiconductor variation with time is numerical simulated. The characteristics of temperature in time and space are also explored. Moreover, the feasibility of obtaining semiconductor parameters by fitting the step response curve is analyzed using the sensitivity and correlation studies of multi-parameters estimation.3. According to step photothermal deflection theory, an experimental platform of step photothermal deflection is set up and experimental debug are also performed. Influences of different experimental conditions and semiconductor material parameters on the photothermal deflection signal are studied. The deflection signal evolutions of detecting light with different distance to the sample surface and with different thermal diffusivity are obtained.