Oscillator strength for intraband transitions in (In,Ga)As/GaAs quantum dots

Abstract

This letter reports on theoretical calculations of the oscillator strength associated with electron intraband transitions in (In,Ga)As/GaAs quantum dots. We study the effect of dot size and lateral separation between adjacent dots on the oscillator strength. The calculations indicate that transitions induced by p-polarized light from the electronic ground state to the first excited state are stronger than those induced by s-polarized light for large size dots with wide lateral interdot spacing. This situation changes, however, for small size dots in close proximity with one another. We discuss the relevance and implication of these results for applications in quantum-dot structures designed for mid-infrared detection.

Quantum wells to quantum dots: 640x512 pixels Long-Wavelength Infrared (LWIR) Quantum Dot Infrared Photodetector (QDIP) imaging focal plane array

“…Fig. 2 normal incidence direction) light, it also absorbs inclined (or side) incidence (z-polarized) light even more strongly [9]. This knowledge has prompted an important design modification, as we now wish to take advantage of the DWELL QDIP's ability to absorb both normal and inclined incidence light in order to maximize quantum efficiency.…”

Demonstration of 640×512 pixels long-wavelength infrared (LWIR) quantum dot infrared photodetector (QDIP) imaging focal plane array

“…At the same time, we also find that the 45°incidence responsivity is 4-5 time stronger than the normal incidence responsivity. This implies that at these wavelengths, the DWELL QWIPs not only have good absorption for normal incidence (x, y-polarized; with z-being the normal incidence direction) light, it also absorbs inclined (or side) incidence (z-polarized) light even more strongly [9]. This knowledge has prompted an important design modification, as we now wish to take advantage of the DWELL QDIP's ability to absorb both normal and inclined incidence light in order to maximize quantum efficiency.…”

“…In a typical detector structure, QD densities are low (compared to the number of dopants in the active regions of QWIPs); so while individual QDs are efficient absorbers, typical QD densities are not high enough to achieve high quantum efficiency. Thus, while QD based infrared detectors have clearly demonstrated normal incidence absorption [5,6], and, in some instances, higher operating temperature as well [5][6][7][8][9][10][11][12], they are still lacking in quantum efficiency and responsivity.…”

Review of current progress in quantum dot infrared photodetectors

“…Apart from making use of p-polarization, by using gratings, research should also be focused on increasing s-polarization absorption. To increase the absorption coefficient in the normal direction, the quantum dot base diameter needs be reduced for greater quantum confinement in the lateral plane, as predicted both theoretically [63] and experimentally [143]. As pointed out by Liu et al [141], strong lateral confinement also means only one or two energy levels in quantum dots.…”

“…Theoretical modeling of quantum dots [21,[59][60][61] has been carried out to analyze and predict quantum dot characteristics measured from photoluminescence (PL), photoluminescence excitation [49], spectral response and absorption studies. The most popular methods include the atomistic pseudopotential approach [62], eight-band k.p analysis [21,59,60,63] based on the valance force field method and numerical simulations based on finite volume methods [64,65]. Various groups around the world have successfully demonstrated good-quality infrared imaging [66][67][68][69][70] with QDIP-based FPAs.…”