Optical absorption of intersubband transitions in In0.3Ga0.7As/GaAs multiple quantum dots

Abstract

Fourier-transform infrared spectroscopy technique was employed to investigate the optical absorption coefficient of intersubband transitions in Si-doped In0.3Ga0.7As/GaAs multiple quantum dot structures. Waveguides with 45° polished facets were fabricated from molecular beam epitaxy grown wafers with different quantum dot size. The measured maximum optical absorption coefficient was found to be in the order of 1.10×104 cm−3. The peak position energy of the intersubband transition was observed to shift toward lower energy when the quantum dot size is increased as expected. The photoluminescence spectra were also measured for different samples with different quantum dot size. The internal quantum efficiency was estimated to be in the order of 58% for a sample with 40 periods of 6 nm dot size.