Study of semiconductor heterostructures with embedded quantum dots: micropillars and photodetectors

Abstract

In this work, we study some of the optical processes that take place into semiconductor systems, specially heterostructures of two types with embedded quantum dots: infrared photodetectors and microcavity pillars. Quantum dots are the source of electrons and/or quase-particles such as excitons and bi-excitons, which are fundamental in the operation of devices based on pillar microcavities and photodetectors. The importance of infrared detectors is enormous, with a huge variety of applications, and the relevance of microcavities have increased due to its promising technological applications. We present here a theoretical and experimental study of these two heterostructures in specific cases of our interest. In order to investigate the coupling between the photonic modes and the emission of quantum dots embedded in microcavity pillars we implemented a code using the free software CAMFR [Peter Bienstmann. Cavity modelling framework, http://camfr.sourceforge.net], which allows to model photonic devices such as VCSELs and microcavities. From the analysis of the intensity of excitation of the modes in the pillars, we showed that it is possible to infer on polarization of the emission of the embedded quantum dots. Furthermore, to help in the interpretation of the response of quantum dot infrared photodetectors, we developed a code on the C-language which is based in a numerical diagonalization of Schr¨odinger equation for the effective mass aproximation, in order to obtain the energy levels and wavefunctions of the system. The oscillator strengths are computed to quantify which are the most probable optical transitions, and to understand some interesting phenomena that appear in the study of infrared photodetectors. We conclude that Auger scattering has a significant role in the response of these devices.