A Theoretical Study of Light Absorption in Self Assembled Quantum Dots

Tarek A Ameen,Yasser M El-Batawy,A A Abouelsaood

doi:10.4236/opj.2013.32b057

Abstract

Self assembled quantum dots have shown a great promise as a leading candidate for infrared detection at room temperature. In this paper, a theoretical model of the absorption coefficient of quantum dot devices is presented. Both of bound to bound absorption and bound to continuum absorption are taken into consideration in this model. This model is based on the effective mass theory and the Non Equilibrium Greens Function (NEGF) formalism. NEGF formalism is used to calculate the bound to continuum absorption coefficient. The results of the model have been compared with a published experimental work and a good agreement is obtained. Based on the presented model, the bound to bound absorption coefficient component is compared to the bound to continuum absorption coefficient component. In addition, the effects of the dot dimensions and electron filling on the bound to continuum absorption coefficient are also investigated. In general, increasing the dot filling increases the absorption and decreasing the dots dimensions will increase the absorption and move the absorption peak towards longer wavelengths.

Highlights

Self assembled quantum dots have attracted the attention due to the promise to improve the performance of many applications, like quantum dot infrared photodetectors (QDIP) [1], [2], and intermediate band solar cells (IBSC) [3]
Non Equilibrium Greens Function (NEGF) formalism is used to calculate the bound to continuum absorption coefficient
The effects of the dot dimensions and electron filling on the bound to continuum absorption coefficient are investigated

Summary

Introduction

Self assembled quantum dots have attracted the attention due to the promise to improve the performance of many applications, like quantum dot infrared photodetectors (QDIP) [1], [2], and intermediate band solar cells (IBSC) [3]. For calculating the bound to bound absorption coefficient of a self assembled quantum dot, a model was presented for the InAS/GaAs QDIP [9]. This model has led to an important result: for QDIP the in-plane polarized absorption is dominant as long as the dot height is not very small compared to its base radius. The effective mass theory is used to build a hermitian Hamiltonian matrix for an isolated self assembled quantum dot Diagonalizing this matrix gives the bound states and energies. A comparison of our model and experimental data of [12] has been done, showing a good agreement

Theoretical Model

G R of the Hamiltonian

Results and Conclusions