Type II quantum wells on GaSb substrate designed for laser-based gas sensing applications in a broad range of mid infrared

Optical properties of InAs/GaInSb/InAs type II quantum wells grown on GaSb substrate have been studied by Fourier transformed photoreflectance and photoluminescence supported by electronic structure calculations. Such a broken gap material system is utilized for the active region of interband cascade lasers and further for laser-based gas sensors operating at room temperature. Based on the measured absorption-like and emission-like spectra in the range from about 2 to above 5 mu m, we indicate the potential of such type II structures for detecting such environmentally relevant gasses as HCI, CO2, N2O, and NH3 which have their absorption lines at wavelengths longer than about 3.5 mu m, i.e. beyond the already explored range characteristic for hydrocarbons. We investigate the issue of the type II transition oscillator strength versus the InAs well width and temperature for two different quantum well layer structures. Significant enhancement of the type II transition intensities could be predicted for W-like design of the well and increasing with temperature, as a consequence of various thermal energy gap coefficients of the involved materials and weakening of the confinement for electrons. The concept of compensating the electric field effect in the real operational device, affecting the transition probability, by intentionally introducing an asymmetry of the double quantum well structure has been shown to be functional for various emission wavelengths. Reasonable values of the transition oscillator strengths could still be demonstrated at about 5 mu m. (C) 2012 Elsevier B.V. All rights reserved.