Effect of modulating field on photoreflectance of surface-intrinsic-n+ type doped GaAs

• Main Authors: Chien-Ju Yin, 簡茹吟
• Other Authors: Dong-Po Wang
• Format: Others
• Language: zh-TW
• Published: 2000
• Online Access: http://ndltd.ncl.edu.tw/handle/50087591425152528262

碩士 === 國立中山大學 === 物理學系研究所 === 88 === Abstracts Photoreflectance(PR) of surface-intrinsic n+ type doped GaAs has been measured for various power densities of pumping laser.The spectra exhibited many Franz-Keldysh oscillations,where by the electric field(F) can be determined from the technique of the fast fourier transform.It is known that F's determined from PR are subjected to photovoltaic effect ,but it is difficult to estimate the strength of modulating field in the PR measurements.Hence we have investigated the relation between F and modulating field by using electroreflectance to simulate PR.In this work,the relation will be confirmed by using solely PR.Here a method was devised to obtain the strength of modulating field in the PR measurements.The photo-voltage(Vs)of the pump beam can be measured directly with a lock-in amplifier by making electrical contacts on the front and rear sides of the sample.The strengh of modulation field is equal to Vs/d due to a uniform F in the undoped layer,where d is the thickness of the undoped layer.