Comparison of strain-compensated quantum cascade lasers grown with GaInAs and InP waveguides

We compare strain-compensated quantum cascade lasers (QCLs) with two different waveguide designs and active regions with and without injector grown with solid source MBE. After installing a phosphorous source in our GEN II system and optimising the growth for thick InP layers, we were able to substitute our previous used GaInAs cladding layer with InP, yielding reduced losses and higher confinement factor. Fabricated devices using an InP waveguide layer revealed low threshold current densities (0.15 kA/cm² at 77 K and 2.47 A/cm² at 300 K) and high-temperature operation up to 490 K in pulsed mode. Injector-free QCLs, called intersubband staircase lasers (SCLs) also benefit from an InP waveguide, leading to an increased maximum operation temperature up to 310 K and a relatively low threshold current density of 6.17 kA/cm² at 300 K.