Room-temperature threshold-current dependence of GaAs-AlxGa1−xAs double-heterostructure lasers on x and active-layer thickness

Abstract

The known properties of GaAs and Al_xGa_1−xAs have been used to calculate the threshold‐current density of double‐heterostructure (DH) lasers at room temperature without adjustable parameters. In the absence of leakage currents due to unconfined carriers, the room‐temperature threshold‐current density for broad‐area DH lasers may be repesented by J_th (A/cm²) =4.5×10³d+(20d/Γ)[α_i+(1/L) ln(1/R)], where d is the active‐layer thickness in microns, Γ is the waveguide confinement factor, α_i is the internal loss, L is the cavity length, and R is the facet reflectivity. The experimentally observed increase of J_th for xxGa_1−xAs (x≲0.3) of ∼1 μm. The above expression for J_th fits Kressel and Ettenberg’s J_th versus active‐layer‐thickness data at x=0.65, while for x=0.3, the experimental J_th is 300 A/cm² larger than the calculated J_th at d=0.1 μm. This difference appears to be due to greater scattering loss at x=0.3 than x=0.6.