Significant developments in mid-infrared lasers have been made in recent ye
ars towards the goal of minimally cooled operation with useful output power
s through the use of type-I structures made from III-V semiconductors. In p
articular, the use of strain in such devices to suppress non-radiative loss
es such as Auger recombination and intervalence-band absorption has shown p
romise. The indium-aluminium-gallium-antimonide (In1-x-yAlxGaySb) materials
system offers an excellent compromise between the requirements for good el
ectronic and optical confinement and those for low series resistance necess
ary for efficient diode laser operation across the 3-5 mum wavelength range
. We present data from diode lasers, grown by molecular beam epitaxy, compr
ising compressively strained InSb-like wells within In1-x-yAlxGaySb confini
ng regions and In1-xAlxSb cladding layers. At 77 K the threshold current de
nsity is less than 50 A cm(-2) and differential efficiency as high as 30% p
er facet for devices with an emission wavelength of 3.4 mum. The maximum te
mperature of operation demonstrated to date is 170 K; however, theory indic
ates that, with optimization of well and barrier parameters, minimally cool
ed operation should be attainable.