Influence of the potential barrier height in a heterojunction laser on the temperature dependence of the threshold current

A theoretical analysis is made of electron diffusion in the active region of a heterojunction laser under conditions of carrier leakage through a heterobarrier of height Δ, radiative recombination in the active region, and surface recombination at the heterointerface. The known temperature dependence of the threshold current of a heterojunction laser without leakage and surface recombination at the heterointerface is used to obtain an expression for the temperature dependence of the threshold j_th(T) subject to these factors. A comparison is made between theory and experiment for InGaPAs/InP and Al_xGa_1-xAs/Al_yGa_1–yAs double-heterostructure lasers. A satisfactory agreement between the theoretical and experimental curves leads to the following conclusions: a) the difference between the band gaps of the heterojunction-forming materials ΔE_g, which is the same as Δ, falls entirely within the conduction band; b) the experimental depence j_th(T) imposes an additional relationship between parameters of the heterojunction-forming materials such as the electron lifetime in the active and passive regions, their diffusion lengths, and the active layer thickness. The electron lifetime in the active region of an InGaPAs/InP heterojunction laser with Δ = 160 meV is estimated to be of the order of 6 nsec.