Short-wavelength intersubband staircase lasers, with and without AlAs-blocking barriers
We present short-wavelength Ga0.322In0.678As/Al0.635In0.365As quantum-cascade lasers without injector regions (staircase lasers), with and without AlAs-blocking barriers, emitting at ~4.55 µm and ~4.2 µm, respectively. By introducing AlAs-barriers into the active region, a thermally activated escape of electrons from the upper laser state into the quasicontinuum is avoided. The sample without AlAs-barriers shows a maximum operating temperature of 220 K with a threshold current density of 4.3 kA cm−2. A sample with an improved design with AlAs-blocking barriers shows threshold current densities of 2.9 kA cm−2 at 220 K and 4.8 kA cm−2 at 300 K. The maximum operating temperature has been increased to 370 K.