<title>Theoretical study of optical properties of III-V compound semiconductor quantum-well structures</title>

Abstract

In the paper, the optical properties of III-V compound semiconductor quantum well structures are studied theoretically. We take into account the nonparabolic valence band structure due to band mixing effect using multiband effective mass theory (K(DOT)P theory). A variational method is used to solve the exciton problem. The calculated exciton peak positions versus electric field show good agreement with the experimental results published in literatures. The optical absorption coefficient and spontaneous emission rate in quantum well structures are calculated using the formula derived by the density matrix formalism with intraband relaxation taken into account. The optical gain and refractive index variation in a quantum well laser structure are calculated by giving equal electron and hole density in the well region. The theoretical results show that the peak position of the gain spectra exhibits a red shift and its amplitude decreases with increasing electric field for both the TE and TM polarization. The gain spectra in our model shows remarkable difference both in the spectra shape and the peak amplitude as compared with those from the conventional models. The peak gain is reduced and the gain spectrum is more symmetric and closer to experimental observations. The refractive index variation in the active region will result in the defocusing effect and increase the optical loss.