Lateral current spreading in unipolar semiconductor lasers

Lateral current spreading in shallow ridge processed unipolar semiconductor lasers is described using a two-dimensional flow model. In these devices, contrary to bipolar diode lasers, the density of carriers can be considered constant also in the active region. Therefore electron diffusion is a negligible effect and the spatial distribution of the current can be obtained by solving a two-dimensional differential equation for the electric potential. Our calculations prove that the major contribution to the current spreading takes place right before electrons enter the active region and is caused by the discontinuity of the conductivity at the cladding–active region interface.