Type-I InSb-based mid-infrared diode lasers

Significant developments in mid-infrared lasers have been made in recent years towards the goal of minimally cooled operation with useful output powers through the use of type-I structures made from III-V semiconductors. In particular, the use of strain in such devices to suppress non-radiative losses such as Auger recombination and intervalence-band absorption has shown promise. The indium-aluminium-gallium-antimonide (In1-x-yAlxGaySb) materials system offers an excellent compromise between the requirements for good electronic and optical confinement and those for low series resistance necessary for efficient diode laser operation across the 3-5 mum wavelength range. We present data from diode lasers, grown by molecular beam epitaxy, comprising compressively strained InSb-like wells within In1-x-yAlxGaySb confining regions and In1-xAlxSb cladding layers. At 77 K the threshold current density is less than 50 A cm(-2) and differential efficiency as high as 30% per facet for devices with an emission wavelength of 3.4 mum. The maximum temperature of operation demonstrated to date is 170 K; however, theory indicates that, with optimization of well and barrier parameters, minimally cooled operation should be attainable.