Isotype $n$-AlGaAs/$n$-GaAs heterostructures optimized for efficient interband radiative recombination under current pumping

Carrier transport in an isotype AlGaAs/GaAs heterostructure optimized for efficient radiative recombination under current pumping is investigated. The features of carrier transport are analyzed using the models of drift diffusion, drift diffusion with field-dependent mobility, and energy balance with field-dependent mobility. It is shown that the radiative-recombination level in the active region at weak currents is higher in the energy balance model due to the more efficient accumulation of carriers generated by impact ionization. This is explained by the velocity overshoot effect at the heterointerface, which is induced by a sharp change in the electron density and the electric field at the heterojunction, whereas in the drift-diffusion approximation, the drift velocity in this region is equal to the saturated one and the potential barrier decreases due to the accumulation of high densities of electrons at the heterojunction. At currents above 40 A, the radiative-recombination level in the active region is higher in the drift-diffusion approximation, which is explained by a stronger electric field and higher impact ionization rate in the layer with the electric-field domain. An increase in the radiative-recombination current in the active region by more than 50% to 13.5 A (at a pump current of 100 A) and in the maximum internal quantum efficiency to 16% (at a current of 40 A) with a decrease in the thickness of the carrier accumulation layer to 100 nm is demonstrated.