Bandgap effects of quantum well active-layer on threshold current density, differential gain and temperature characteristics of 1.3 μm InGaAlAs/InP quantum well lasers

Quantum-well (QW) active-layer effects on the threshold Current density, the differential gain, and the characteristic temperature of lattice-matched (LM), compressive-strained (CS) and strain-compensated (SC) 1.3 mum InGaAlAs/InP QW lasers are theoretically investigated. The calculations are executed by changing the well bandgap from 0.80 to 0.90 eV, while the well widths are adjusted to keep emission wavelength unchanged. The calculation results are analyzed by introducing characteristic parameters such as subband energy spacing, squared optical matrix elements, average effective hole mass, potential depth and subband numbers. From these procedures, it is revealed that SC-QW lasers have lower threshold current density, higher differential gain and better temperature performance compared to CS or LM-QW lasers. Furthermore, there is an optimum well bandgap for better characteristic temperature which is very closely related to the subband numbers in QW.