A model and analysis of intermixed 980 nm InGaAs/GaAsP MQW VCSEL

Abstract

Inter-mixing in a hypothetical InGaAs/GaAsP multi-quantum vertical cavity surface emitting laser (VCSEL) designed for emission at 980 nm has been mathematically modeled and analyzed. The solution to the diffusion equation using a combined superposition of the error-function describing the disordering process for the whole VCSEL structure has been applied. The simulation results showed no significant change in the reflectivity of the VCSEL top and bottom distributed Bragg reflectors (DBRs) at diffusion lengths of up to 10 nm. However, the results revealed that the VCSEL DBRs mirror loss have been more than doubled at the same diffusion length. The VCSEL effective cavity length has been shown to significantly increase by 200 nm for a diffusion length of 10 nm as compared to that of the as-grown VCSEL. The VCSEL active region relative confinement factor has been shown to appreciably decrease as a function of diffusion length. The VCSEL threshold current and external differential quantum efficiency have been derived as a function of diffusion length and were found to reliably describe the intermixing process in VCSELs. The model presented in this article could provide a mean to describe the compositional grading process in VCSELs and may reliably predict their various optical and electrical parameters.