Improving device performance of type-II interband cascade lasers with room temperature emission wavelengths below 3 μm

We report the demonstration of hybrid-cladding interband cascade lasers (ICLs) for a room temperature emission wavelength range from 2.68 to 2.9 μm. Their threshold current density and threshold input power density are substantially lower than previously reported values from superlattice-cladding ICLs at similar wavelengths. These ICLs were able to operate in pulsed modes at temperatures close to 400 K. At 300 K, the threshold current density was as low as 191 A/cm2 with a threshold input power density of 693 W/cm2. Narrow ridge devices lased in a continuous wave (cw) mode at room temperature and above with threshold current density and output power that are improved compared to previous ICLs at similar wavelengths. Comparative studies of devices with different local material qualities from the same wafer and different wafers revealed a certain correlation between Shockley–Read–Hall recombination and threshold current density, which shed light on understanding the degradation of device performance with the shortening of the lasing wavelength of type-II ICLs. Additionally, negative differential conductance features were observed under reverse bias voltage, which may provide an interesting and potentially useful means to examine the material and fabrication qualities of devices with some extended applications.