半導體奈米結構分散性群體的磁性與磁光特性

Abstract

對於半導體元件多功能的日益需求促使了形狀複雜的半導體奈米物件的發展，其展現出無論在光、電、量子資訊、生醫影像的發展性。然而，奈米物件本身複雜的變異性(形狀、大小、組成)造成其物理性質上的極大變異；為了對半導體奈米物件有更深的了解和更精確的掌握，我們發展出一套一般性的理論描述半導體奈米物件的物理響應，此理論根據多變異分布函數可描述不同的物理性質的變異。在此報告中，我們計算了半導體奈米物件的能階和其對應之電子電洞波函數，並考慮其形狀、物質參數和分布上的變異。為了驗證我們的方法，我們對ZnTe/CdSe的量子點和InAs/GaAs量子環做光譜和磁化率的模擬，其結果和實驗所得數據相符。因此我們的這一套理論方法將給予最佳化奈米物件的平均物理特性很大的幫助。

Current demand for multiband and multifunctional nano-based semiconductor devices stimulates the development of novel nano-scale semiconductor components (nano-objects). Impressive progress in semiconductor technologies makes it possible to fabricate semiconductor nano-objects with very sophisticated shapes and material compositions: quantum dots, quantum dot molecules, quantum dot posts, and quantum rings, etc. The semiconductor nano-objects demonstrate unique properties those are very promising for modern optics, optoelectronics, quantum information processing, bio and medical imaging, etc. Unfortunately, the inherent dispersion of parameters (shape, size, material composition) leads to fluctuations (some time almost uncontrollable) of the physical properties of macro-systems combined from the nano-objects. To achieve a proper quantitative description and address the controllably of macro characteristics of ensembles of the semiconductor nano-objects in this study we have proposed and developed a general theoretical description of the physical response of dispersive ensembles made from the semiconductor nano-objects of complex geometries and material compositions. The description is based on the multivariate distribution function, which cumulatively reproduces variations of the objects’ parameters.In this report we present and discuss our method of multivariate simulation of physical properties of ensembles of semiconductor nano-objects with dispersion in geometry, material parameters, and spatial distributions. Using the mapping method (recently derived by us) we are able to very efficiently compute energy states and wave functions of electrons and holes confined in the nano-objects within a wide range of sizes, shapes, and compositions. Thus, using the hybrid multiscale (hierarchical) method we are able to simulate ensembles of nano-objects with multiparametric (multivariate) distributions. To demonstrate our method efficiency we simulated the absorption cross section of ensembles of ZnTe/CdSe core/shell quantum dots and the unusual diamagnetic response (magnetic susceptibility) of ensembles of wobbled InAs/GaAs quantum rings. We have theoretically obtained the actual optical spectra and magnetic susceptibility in a very good agreement with experimental data. We have proven that our multivariate statistical approach can be useful for optimization of the averaged physical characteristics of the dispersive ensembles of nano-objects.