Investigation of high optical gain in complex type-II InGaAs/InAs/GaAsSb nano-scale heterostructure for MIR applications.

This paper reports a comprehensive theoretical study of W-shaped complex type-II InGaAs/InAs/GaAsSb nano-scale heterostructure consisting of two quantum wells of InAs material using the six-band k.p theory. The entire structure has been supposed to be grown on InP substrate. In order to optimize the optical gain, the probability densities of electrons and holes were optimized in the heterostructure. Following these calculations, dispersion relations for electron and hole energies, and transverse electric and transverse magnetic polarizations dependent dipole matrix elements and momentum matrix elements were calculated and, finally, the optical gain in both polarization modes was calculated. For this optimized complex heterostructure, a very high optical gain of the order of ∼4500  cm in the regime of mid-infrared wavelength ∼3.2  μm has been achieved. The results suggest that the designed nano-heterostructure may be utilized for mid-infrared region (MIR) applications such as chemical and bio-molecular sensing of molecules, for the applications of spectroscopy in the "fingerprint region" of molecular science, and for detection of atmospheric gases that respond to 3.2 μm wavelength.