InAs-based interband-cascade-lasers emitting around 7  μ m with threshold current densities below 1 kA/cm2 at room temperature

Interband cascade lasers (ICLs) grown on InAs substrates with threshold current densities below 1 kA/cm2 are presented. Two cascade designs with different lengths of the electron injector were investigated. Using a cascade design with 3 InAs quantum wells (QWs) in the electron injector, a device incorporating 22 stages in the active region exhibited a threshold current density of 940 A/cm2 at a record wavelength of 7 μm for ICLs operating in pulsed mode at room temperature. By investigating the influence of the number of stages on the device performance for a cascade design with 2 QWs in the electron injector, a further reduction of the threshold current density to 800 A/cm2 was achieved for a 30 stage device.