Carrier dynamics in (Ga,In)(Sb,Bi)/GaSb quantum wells for laser applications in the mid-infrared spectral range

Abstract

We present experimental studies on low-temperature (T={4.2}hbox { K}) carrier dynamics in (Ga,In)(Sb,Bi)/GaSb quantum wells (QWs) with the nominal In content of 3.7% and the Bi ranging from 6 to 8%. The photoreflectance experiment revealed the QW bandgap evolution with -{33}pm {1}hbox { meV}/hbox {at} % Bi, which resulted in the bandgap tunability roughly between 629 and {578}hbox { meV}, setting up the photon emission wavelength between 1.97 and {2.2},upmu hbox {m}. The photoluminescence experiment showed a relatively small 3–10hbox { meV} Stokes shift regarding the fundamental QW absorption edge, indicating the exciton localisation beneath the QW mobility edge. The localised state’s distribution, being the origin of the PL, determined carrier dynamics in the QWs probed directly by the time-resolved photoluminescence and transient reflectivity. The intraband carrier relaxation time to the QW ground state, following the non-resonant excitation, occurred within 3–25hbox { ps} and was nearly independent of the Bi content. However, the interband relaxation showed a strong time dispersion across the PL emission band and ranging nearly between 150 and {950}hbox { ps}, indicating the carrier transfer among the localised state’s distribution. Furthermore, the estimated linear dispersion variation parameter significantly decreased from Delta tau approx {20} to {10}hbox { ps}/hbox {meV} with increasing the Bi content, manifested the increasing role of the non-radiative recombination processes with Bi in the QWs.