Tuning In0.3Ga0.7As∕GaAs multiple quantum dots for long-wavelength infrared detectors

Abstract

Optical absorption spectra of intersubband transitions in ${\mathrm{In}}_{0.3}{\mathrm{Ga}}_{0.7}\mathrm{As}∕\mathrm{GaAs}$ multiple quantum dots were investigated using the optical absorption as a function of the number of ${\mathrm{In}}_{0.3}{\mathrm{Ga}}_{0.7}\mathrm{As}$ monolayers deposited using the molecular-beam epitaxy Stranski–Krastanow technique. The peak position energy reached $13.7\mu \mathrm{m}$ for a sample containing 50 monolayers of ${\mathrm{In}}_{0.3}{\mathrm{Ga}}_{0.7}\mathrm{As}$ . The lack of the observation of intersubband transitions in small quantum dots, where the number of the deposited monolayer is less than 15 monolayers, is an indication of the absence of quantum confinement. On the other hand, the presence of high dislocations density in larger quantum dots, where the deposited number of monolayers exceeds 50, could be the reason of why the intersubband transitions are degraded.