BASIC DESIGN PRINCIPLES FOR INGAASP/INP STRAINED-LAYER SINGLE-QUANTUM-WELL LASERS

We describe the effects of strain (both tension and compression) on device performance measures, such as optical gain, threshold carrier density, radiative current density, and differential gain, for 1.3-mum InGaAsP/InP strained-layer single-quantum-well (SL-SQW) lasers. An InGaAsP quaternary active layer is found to provide more freedom in design than an InGaAs ternary active layer because the amount of strain and the quantum-well thickness can be independently determined in an InGaAsP system for a given emission wavelength. The essential features of strain-induced changes in the valence band structures are extracted from the k.p results and are then directly correlated to the performance of SL-SQW lasers. The application of biaxial tension is shown to significantly enhance the optical gain and differential gain as compared with compressive strain. Both threshold carrier density and radiative current density are reduced compared to those of unstrained structures by the application of either type of strain. On the basis of the characteristic features of strain-induced changes in the valence band structures, basic design principles for improving performance of InP-based SL-SQW lasers are discussed.