Density-dependent intersubband absorption in strongly disordered systems

Abstract

We study theoretically the intersubband ͑IS͒ absorption spectrum of electrons in a center-doped quantum well ͑QW͒ as a function of the carrier density. Besides the subband quantization in z direction, the wave functions of the electrons, being directly exposed to the charged dopands, become disorder localized in the layer plane. For each set of random impurity configurations, the corresponding spectrum of quantum states is computed with a self-consistent density-functional approach, thus, taking into account the disorder and nonlinear static screening effects in a realistic way. On the basis of these effective single-particle states, we then include dynamic many-body effects ͑depolarization and dynamic exchange corrections͒ by applying and extending our recently developed theory of resonant screening in the localization regime. We analyze the relevance of the various many-body effects and find that at higher electron densities the direct static Hartree and the depolarization contributions dominate over the exchange effects. Dynamic Coulomb interactions qualitatively change the IS absorption spectrum of the statically screened electron gas, however, do not lead to a spectral narrowing in this system. A small variation of the ␦n-layer position within the QW affects the relative disorder strength of the two subbands and causes dramatic changes of the spectral shape and width. Our model and results are suitable for a direct comparison with experimental data.

Intersubband absorption linewidth in GaAs quantum wells due to scattering by interface roughness, phonons, alloy disorder, and impurities

“…Note here that the z-integrals of ζ 0 (z) 4 , ζ 1 (z) 4 , and [ζ 0 (z)ζ 1 (z)] 2 have comparable values (3/2L, 3/2L, and 1/L, respectively in the infinite-barrier approximation); thus Γ intra (E) and Γ inter (E) are nearly equal, and 2Γ op (E), the sum of them, is comparable with 2Γ tr (E). Figure 5 shows 2Γ op (E), Γ intra (E), Γ inter (E), and 2Γ tr (E) at T = 300 K. Γ intra (E) and Γ inter (E) have almost the same constant values of about 0.5 meV.…”

Interface-roughness-induced broadening of intersubband electroluminescence in p-SiGe and n-GaInAs∕AlInAs quantum-cascade structures

“…Note that the spectral shape of the absorption is also affected by nonparabolicity, electron-electron interactions, 16,17 other scattering mechanisms, and disorder. 18,19 The detailed consideration of these effects is beyond the scope of this letter.…”

Controlling a cluster of interacting quantum dot molecules by laser pulses – a computer experiment

“…In the framework of disorder-localized intersubband systems, the theory of Coulomb-coupled two-level oscillators has already been investigated in some detail in Refs. [5] and [6]). To describe the dynamics of the interacting oscillators in response to the driving laser fields we solve the coupled density-matrix equations of the two-level systems in the time domain.…”