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Excitonic complexes in InAs/InP nanowire quantum dots
摘要： InAs quantum dots embedded in InP nanowires form an important platform for basic research studies, as well as for quantum dot applications. Notably, understanding of nanowire quantum dot spectral properties is essential in both cases. Therefore, in this work we use atomistic theory to study spectra of the single exciton (X ), the biexciton (X X ), the triexciton (X X X ), and the positively and negatively charged trions (X + and X ?) con?ned in these nanostructures. We focus on the role of vertical and lateral con?nement, therefore, we systematically study a large family of quantum dots with different heights and diameters, and ?nd the important role of correlations due to presence of higher states. We ?nd that the order of excitonic binding energies is a characteristic feature of InAs/InP nanowire quantum dots being (ordered from negative to positive values): X ?, X X , and X +, with strongly bound X ?, rather weakly bound X X , and typically unbound X +. Next, we determine the key role of alloy randomness due to intermixing, which turns out to especially important for larger quantum dot heights and phosphorous contents over 40%. In selected cases, the alloying can lead to an unbound biexciton, and can even reverse ordering of excitonic lines.
关键词： InAs/InP nanowire quantum dots,atomistic theory,binding energies,alloy randomness,excitonic complexes
更新于2025-09-23 15:21:01
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Atomistic theory of electronic and optical properties of InAsP/InP nanowire quantum dots
摘要： We present here an atomistic theory of the electronic and optical properties of hexagonal InAsP quantum dots in InP nanowires in the wurtzite phase. These self-assembled quantum dots are unique in that their heights, shapes, and diameters are well known. Using a combined valence-force-field, tight-binding, and configuration-interaction approach we perform atomistic calculations of single-particle states and excitonic, biexcitonic, and trion complexes as well as emission spectra as a function of the quantum dot height, diameter, and As versus P concentration. The atomistic tight-binding parameters for InAs and InP in the wurtzite crystal phase were obtained by ab initio methods corrected by empirical band gaps. The low energy electron and hole states form electronic shells similar to parabolic or cylindrical quantum confinement, only weakly affected by hexagonal symmetry and As fluctuations. The relative alignment of the emission lines from excitons, trions, and biexcitons agrees with that for InAs/InP dots in the zincblende phase in that biexcitons and positive trions are only weakly bound. The random distribution of As atoms leads to dot-to-dot fluctuations of a few meV for the single-particle states and the spectral lines. Due to the high symmetry of hexagonal InAsP nanowire quantum dots the exciton fine structure splitting is found to be small, of the order a few μeV with significant random fluctuations in accordance with experiments.
关键词： fine structure splitting,electronic properties,optical properties,emission spectra,tight-binding,single-particle states,excitonic complexes,InAsP quantum dots,InP nanowires,wurtzite phase,configuration-interaction,valence-force-field,atomistic theory
更新于2025-09-23 15:19:57