Monte Carlo analysis of the carrier relaxation processes in linear and parabolic-GRINSCH quantum well laser structures

The carrier relaxation process is widely acknowledged to have a strong bearing on the modulation limit of quantum well lasers. As a first and crucial step toward achieving a better understanding of this phenomenon, we have developed a numerical technique to study such processes in graded-index separate confinement heterostructure quantum well laser structures having an arbitrary grading profile. We base our approach on ensemble Monte Carlo simulation of the carrier transport in the 3-D graded-index region and in the 2-D quantum well. We also introduce a technique to handle the carrier capture and re-emission processes within the Monte Carlo method. The results obtained from our calculations for a number of structures with quantum well sizes 50-100 Å indicate that the overall carrier capture time is about 5-7.5 ps under low injection condition for the linearly graded structures, and significantly longer for the parabolically graded structures. On the other hand, the carrier capture efficiency is found to be higher for the parabolic graded-index structures. We also compare our calculations to published experiments and find good agreement