Influence of injector doping concentration on the performance of InP-based quantum cascade lasers

The influence of injector doping concentration N(inj) on the performance of InP-based quantum-cascade (QC) lasers is investigated for devices emitting around 9.2-µm wavelength and injector doping concentrations between 1 x 10(exp 17) cm-3 and 3 x 10(exp 17) cm-3. The threshold current density, the dynamic range, the maximum emitted output power as well as the maximum operating temperature are found to increase with increasing N(inj). All in all, there exists no optimal value of N(inj) per se. In fact, the injector doping concentration has to be adjusted individually depending whether emphasis is placed on obtaining low threshold current densities or on high-power operation.