Low threshold InAs-based interband cascade lasers grown by MBE

Mid-infrared interband cascade laser (ICL) structures aimed for emission at room temperature in the 4–5 μm wavelength region are grown by molecular beam epitaxy (MBE) on InAs substrates. High crystalline quality of the epitaxial structures has been confirmed by X-ray diffraction with thickness deviations less than 1% from the designs. Also, the average surface defect density is in the low ten to the fourth level. The broad-area (BA) devices made from the MBE-grown ICL wafers can lase in continuous wave (CW) mode in a wavelength range from 3.5 to 4.8 μm at temperatures up to 257 K, which is the highest reported for BA InAs-based ICLs at similar wavelengths. Their threshold current densities are low (e.g. 2.7 A/cm² at 80 K), indicating excellent material quality with a very low Shockley-Reed-Hall recombination. In pulsed mode, the lowest threshold current density is 252 A/cm² at 300 K, and the maximum operating temperature has reached 379 K. By comparisons in device performance among multiple MBE-grown ICL wafers, the importance of beam equivalent pressure stability and accurate control of layer thicknesses is demonstrated for the desirable performance.