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 mu m 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 To of around 22 K above 90 K, whic h indicates that Auger recombination is dominant, but To increasing to arou nd 45 K at lower temperatures. This increase is consistent with a decrease in Auger recombination with decreasing temperature. Using the all InSb devi ce, 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 distribut ion at the Landau level energies. This enabled them to study the effects of a 'quasi'-quantum wire structure with an easily variable degree of confine ment. A reduction in the threshold current I-th with B-field of up to 30% w as 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 o bserved at exactly the field positions where the conduction band Landau lev el separation is resonant with the LO-phonon energy, giving enhanced electr on cooling. Between the resonances the light output was suppressed due to t he effect of the 'phonon bottleneck'. Finally, the size of a real wire, cor responding to the Landau confinement which gives the greatest improvement, has been estimated to be 800 Angstrom.