OPTIMIZATION OF 1.3-MU-M INGAASP COMPRESSIVELY STRAINED-QUANTUM-WELL LASERS

A theoretical study of the performance of compressively strained InGaA sP/InP multiple quantum-well lasers emitting at 1.3 mu m has been carr ied out to investigate the important factors and trends in the thresho ld current density and differential gain with strain, well width and w ell number. We consider structures with a fixed compressive strain of 1 % but variable well width, and also with a fixed well width but vari able strain from 0 % to 1.4 %. We find that there is little benefit to having compressive strains greater than 1 %. For structures with a fi xed 1 % compressive strain and unstrained barriers we find that the op timum structure for lowest threshold current density and a high differ ential gain consists of six 35 Angstrom quantum-wells. In addition, we examine compensated strain (CS) structures with compressive wells and tensile barriers. We show that the conduction band offset can be sign ificantly increased and the valence band offset reduced in such struct ures, to give band offset ratios comparable with aluminium-based 1.3 m u m devices. Our gain calculations suggest that there is little degrad ation in the threshold carrier density or differential gain due to the se alterations in the band offsets; and hence we might expect better l aser performance due to a reduction in thermal leakage currents due to the improved electron confinement.