Influence of Auger and LO-phonon scattering on bulk and `quasi´-quantum wire mid-IR laser diodes

Measurements of the light-current characteristics of bulk InSb on InSb and InAlSb on InSb lasers, emitting at 5.1 μm at 77 K, have been made in the temperature range from 4.2 to 110 K. For the alloy device the authors find values of the characteristic temperature T₀ of around 22 K above 90 K, which indicates that Auger recombination is dominant, but T₀ increasing to around 45 K at lower temperatures. This increase is consistent with a decrease in Auger recombination with decreasing temperature. Using the all InSb device, the authors have applied magnetic fields along the cavity direction at 4.2 K, in order to change the density of states (DOS) to a peaked distribution at the Landau level energies. This enabled them to study the effects of a `quasi´-quantum wire structure with an easily variable degree of confinement. A reduction in the threshold current I<sub>th</sub> with B-field of up to 30% was seen. The most striking results were obtained when the current was kept constant and the magnetic field was swept. Peaks in the light output were observed at exactly the field positions where the conduction band Landau level separation is resonant with the LO-phonon energy, giving enhanced electron cooling. Between the resonances the light output was suppressed due to the effect of the `phonon bottleneck´. Finally, the size of a real wire, corresponding to the Landau confinement which gives the greatest improvement, has been estimated to be 800 Å