Research On The Strain Properties Of InAs Self-organized Quantum Dot Heterostructures

Quantum dots have been demonstrated to have superior properties than the quantum well, such as the smaller threshold current and better quantum confinement effect. In recent years, many researchers have been devoting to fabricating quantum dots which are suitable for optical communications (the emission wavelength of which is 1.3-1.55μm). Now, quantum dot lasers with the 13μm emission wavelength have been achieved, but the quantum dot lasers with 1.55μm emission wavelength are difficult to fabricate by traditional methods. In the growth process of the quantum dots, strain is the driving force and has great impact on the growth and emission wavelength of quantum dots. Therefore, research on the strain distribution of the quantum dots is important for the red-shift the emission wavelength of quantum dot.The main purpose of this paper is to explore the strain distribution by adding different layer in InAs quantum dots. The main contents are listed as follows:1) The strain distribution of the InAs quantum dot with different InGaAs strain reducing layer was calculated using the finite element method. Studies have shown that InGaAs strain reducing layer can reduce the strain of InAs quantum dots. The more In composition and the thicker of the InGaAs layer, the more strain of InAs quantum dots was reduced. For example, when the thickness of In0.3Ga0.7As stress reducing layer are 2.5nm, 5nm and 10nm, the band gap of InAs quantum dots reduced 15mev,23mev, 33mev, respectively.2) The effect of the graded InxGa1-xAs layer on the distribution of the strain was studied by calculating the strain using the finite element method. Three models were established:(1) the graded InGaAs layer was inserted on the top of the InAs quantum dots. (2) the graded InGaAs layer was inserted below the InAs quantum dots. (3) the graded InGaAs layer was inserted both on and below the InAs quantum dot. The results demonstrated that the graded InxGa1-xAs layer can reduce the strain and thus lead to the longer emission wavelength.3) The effect of the GaAsSb strain reducing layer on the distribution of the strain was studied using the finite element method. The results showed that the band gap of InAs quantum dot decreased by 13meV,24meV and 34meV when the thickness of the GaAs0.7Sb0.3 strain reducing layer was 2.5nm,5nm and 10nm, respectively. And the results also showed that both the thickness and the Sb composition of the GaAsSb layer were the important factors for the strain distribution.4) The effect of the InGaAs strain reducing layer on the strain distribution of the InAs/InP quantum dot was studied using the finite element method. The results showed that the strain of the InAs/InP quantum dot was reduced by increasing the In composition. And the thicker of the high In composition capping layer, the more strain of the InAs/InP quantum dots was reduced.5) The InAs quantum dots with GaAs and InGaAs capping layer were grown with other cooperators. And the results showed that the emission wavelength of quantum dots with InGaAs capping layer was shifted to 1.3μm.