Effect of surface recombination velocity on the threshold current and differential quantum efficiency of the surface-emitting laser diode

Threshold current and quantum efficiency of the surface-emitting laser diodes were calculated on the basis of a planar carrier diffusion model with cylindrical boundary and analytical electromagnetic field distribution in either a uniform core waveguide or Vainshtein´s open cavity model. Surface recombination at the boundary of the quantum-well active region was much greater than the bulk recombination in both structures unless cavity diameter was greater than 50 μm. Diffraction loss was also significant in the open cavity structure as cavity diameter decreased. Reducing the surface recombination velocity leads to the reduction of threshold current and enhancement of differential quantum efficiency. In order to further reduce that current, using a buried heterostructure with a vertical waveguide structure is suggested