Optical and Spectral Characterization of Sub-monolayer QDIPs

In this chapter, we have explored the properties of an unconventional type of quantum dots, namely sub-monolayer (SML) quantum. We have performed a systematic study to optimize different growth parameters and have investigated structural and optical properties of the materials. We have successfully demonstrated high device performance of sub-monolayer quantum dots infrared photodetector with confinement-enhancing (CE) barrier and compared with conventional Stranski–Krastanov quantum dots with a similar design. This quantum-dots-in-a-well structure with CE barrier enables higher quantum confinement and increased absorption efficiency due to stronger overlap of wave-functions between the ground state and the excited state. Normal incidence photoresponse peak is obtained at 7.5 µm with a detectivity of 1.2 × 1011 cm Hz1/2 W−1 and responsivity of 0.5 A/W (77 K, 0.4 V, f/2 optics). Using photoluminescence and spectral-response measurements, the band structure of the samples was deduced semi-empirically.