RADIATIVE PERFORMANCE OF STRAINED-LAYER LASERS

It is shown that application of biaxial tension to the active region o f a bulk-like III-V semiconductor laser can significantly enhance TM g ain compared to TE gain and reduce the threshold current density, owin g to improved suppression of spontaneous emission polarised in the gro wth plane of the laser structure. The differential gain is enhanced co mpared to unstrained structures, and a larger peak gain can be achieve d than in comparable structures under biaxial compression. The authors include the spin-split-off band in their calculations and show that t he strain-induced interaction with this band has a significant influen ce on the character of the valence states, particularly in tensile-str ained structures. Using idealised quantum-well calculations, the autho rs investigate the effect of changing the valence band mass m(v) with respect to the conduction band mass and how this affects the radiative properties of a laser structure. It is shown that, although it is ind eed the case that the transparency carrier density always increases wi th increasing m(v), for the authors' ideal model, the radiative curren t density can decrease.