Theoretical study of strained InGaP quantum-well lasers

The effects of biaxial compressive and tensile strains on the optical gain and threshold current density of 70 Å strained InGaP-In(AlGa)P quantum-well lasers are studied theoretically. Due to strain effects on the density of states and optical dipole matrix elements, compressive strain produces the largest gain (TE) for carrier density N<5×10¹⁸ cm^-3 while the TM mode gain of a tensile strained quantum well is the largest when N>5×10¹⁸ cm^-3. Calculated threshold current densities of compressive- and tensile-strained quantum wells are both lower than unstrained case. For cavity length longer than 500 μm, a quantum well with compressive strain has the lowest threshold current density. In this case, calculated threshold density shows reasonable agreement with the experiment.