Graded index SCH transistor laser: Analysis of various confinement   structures
  New configuration of confinement structure is utilized to improve optoelectronic performances, including threshold current, AC current gain as well as optical bandwidth and optical output power of single quantum well transistor laser. Considering the drift component in addition to the diffusion term in electron current density, a new continuity equation is developed to analyze the proposed structures. Physical parameters including, electron mobility, recombination lifetime, optical confinement factor, electron capture time and photon lifetime is calculated for new structures. Based on solving continuity equation in separate confinement heterostructures, threshold current reduces 67% and optical output power increases 37%. 
Mohammad Hosseini, Hassan Kaatuzian, and Iman Taghavi
cond-mat.mes-hall physics.optics