Theory for intersubband absorption in quantum dots

Quantum-dot infrared photodetectors (QDIPs) have been researched intensively because normal incidence absorption of the quantum dot layer is possible, unlike quantum-well infrared photodetectors (QWIPs) which require a grating coupled structure or an off-normal incidence configuration to satisfy the polarization selection rules. In this paper, we present a theoretical model for the band structure of a strained quantum dot, modeled as a quantum disk, and the intersubband absorption. We first present analytical expressions for the polarization-dependent optical dipole moments and then calculate the absorption spectra for various carrier densities and temperatures. The effects of carrier density, temperature, and inhomogeneous broadening will be discussed.