Abstract
The effects of biaxial strain produced by the lattice mismatch of constituent materials on the optical properties of strainedIn1−xGaxAsyP1−y/In1−xGaxAsquantum well lasers are investigated.The optical gain and refractive index change of a biaxially stressed quantum well lasers are studied theoretically using the multiband effective mass equation (i.e.,k→⋅p→method), deformation potential theory and Fermi-Golden rule, band mixing effect is retained in the calculations. It is found that the biaxial strain would change the subband structures and optical properties of quantum well lasers, we found the gain of TE mode increases with increasing compressive strain, while the gain of TM mode increases with increasing tensile strain, these will be benefited for reducing the threshold current depending on whether the quantum well lasers are operating in TE or TM mode. On the other hand, the refractive index change in the active region near the TE(TM) mode peak gain becomes more negative when a biaxial compressive(tensile) strain is applied, it leads to the conclusion that the strain weakens the optical confinement, the temperature dependence of gain also becomes stronger when there is strain.Finally, we also found the minimum peak gain occurs when a small tensile strain is applied, but no strain.
Highlights
When the lattice mismatch of constituent materials is greater than 0.1%, we called such semi-conductor materials are lattice-mismatched.Previous heterostructure work is primarily focused on lattice-matched system due to the degradation of electronic and optical properties of devices made from lattice-mismatched material systems
The effects of the biaxial strain produced by the lattice mismatched of constituent materials on the optical gain in quantum well lasers are investigated, the refractive index change be calculated in order to understand the guiding behavior of laser light in the active region
Once the subband levels and wavefunctions are known, the optical gain g(w) and refractive index change (An,./n,) derived based on Fermi-Golden rule with broadening effect taken into account are: (8)
Summary
When the lattice mismatch of constituent materials is greater than 0.1%, we called such semi-conductor materials are lattice-mismatched. Previous heterostructure work is primarily focused on lattice-matched system due to the degradation of electronic and optical properties of devices made from lattice-mismatched material systems. The theoretical studies are focused on uniaxially stressed quantum wells [8,9,10], there will be valuable to realize the electronic and optical properties of strained-layer quantum wells, but unrealistic in device applications. The effects of the biaxial strain produced by the lattice mismatched of constituent materials on the optical gain in quantum well lasers are investigated, the refractive index change be calculated in order to understand the guiding behavior of laser light in the active region. Once the subband structures and wave functions are obtained, the gain and refractive index change can be calculated based on Fermi-Golden rule [11] with the broadening effect taken into account
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