Research On 60°-type Threading Dislocation Bending In GaAs/Si Heteroepitaxy With InAs/GaAs Quantum Dot

With the advent of the era of big data and the rapid growth of internet information,communication networks are required to develop towards the direction of high speed and large capacity.Due to the limitation of transmission bandwidth and power consumption,the traditional electrical interconnection has been unable to meet the development requirements of high-performance chips,and integrated optical interconnection on silicon is considered as one of the effective ways to solve these problems.As the core device of optoelectronic integration,the lasers made on GaAs/Si template can combine the advantages of the two materials,which is widely used in the high-bandwidth optical interconnection field.Not only the desirable compatibility with CMOS integrated circuits can be obtained,but also the preferable luminous performance can be realized.However,high-density threading dislocations(TDs)appear in the epitaxial growth process due to the substantial difference of lattice constants between the two materials,which seriously degrade the performance of lasers made on this template.As three-dimensional stress structures,quantum dots(QDs)have strong stress field.A very strong Peach-Koehlor force will bend the dislocation energetically when a TD propagates close to a QD.And according to our previous reports,the insertion of InAs/GaAs QDs dislocation filters in the process of GaAs/Si epitaxial growth can effectively impede the propagation of TDs and thus reduce TDs density in the epilayer.However,the theoretical research on TD bending with QDs is still insufficient that the effect of dislocation filters is unable to anticipate before the crystal growth.Evaluating the bending capability can not only help us to improve the performance of QDs dislocation filters so as to avoid the poor effect in the experiment,but also can shorten the experiment time and reduce cost.Based on the above reasons,this paper focuses on the numerical study of 60°-type TDs bending in GaAs/Si heteroepitaxy with InAs/GaAs QDs.The dislocation blocking system with InAs/GaAs QDs is simulated by finite element method,and the methods to evaluate the bending capability of single-layer QDs and multi-layer QDs are proposed.The results offer guidelines for the design of QD dislocation filters and provide an important step towards the realization of photonic integration circuits on silicon.Innovative results are described as follows:(1)The effects of the cap layer thickness and the QD base width are discussed.It is found that both of the two factors have positive effects on TD bending:on one hand,in order to enhance the bending area ratio of a single QD(the bending area divided by the area of the QD base)from 81%to 96.04%,the cap layer thickness has to increase from 5 nm to 9.2 nm;on the other hand,with the base width increasing from 8 nm to 26 nm,the bending area ratio of a single QD will rise from 60.06%to 88.07%.(2)The methods to evaluate the bending capability of single-layer QDs and multi-layer QDs are proposed.For QDs with the height of 4 nm and the density of 1011 cm-2,the bending area ratio of single-layer QDs(the bending area divided by the area of the QD layer)increases from 3.02%to 46.76%with the base width rising from 8 nm to 26 nm.For QDs with the base width of 26 nm,the height of 2.5 nm and the cap layer thickness of 38 nm,taking the density of 5×1010 cm-2 into account,the dislocation blocking ratio(TDs impeded by QDs dislocation filters divided by initial TDs)of three-layer QDs is about 60.3%,and the ratio is up to 78.54%with five-layer embedded QDs.