Research On Material Growth And Device Fabrication Process Of ?-? Compound Semiconductor Lasers On Si

In the past decade,information industry developed rapidly,thus the optical communications systems are facing a huge challenge.The emitters and the receivers used in the optical communications system contain many optoelectronic devices.Therefore,the performances of optoelectronic devices play an important role in determining the overall performance of optical communications system.Meanwhile,ultra-large-scale integrated circuits on Si have been fully developed,and it is the basis of the electronic terminal of the modern communication network.If the integration of photonic devices and silicon-based microelectronic devices can be achieved(ie,photoelectron integration),the connection between the optical communication network and the electronic terminal will be more compact.At the same time,the wide bandwidth,high transmission rate,and high anti-interference ability for optoelectronic devices are also utilized.With the long-term efforts of researchers,many silicon-based optical devices,such as silicon-based detectors,silicon-based optical modulators,etc.,have been successfully applied,but silicon-based lasers have made slow progress.For optoelectronic integration,the most severe challenge is the practical application of lasers on Si.However,silicon is an indirect band material and dose not have good luminescent properties,which limit its applications in luminescent devices.Based on the above background,our work is devoted to fabricating directly epitaxial III-V compound semiconductor lasers on Si,which can solve the problem of silicon-based light sources.The thesis focuses on the research for material growth and device fabrication of silicon-based lasers.The main researches and achievements are as follows:(1)The work of the thesis is based on our previous achievement on the three-step growth method(The dislocation density of GaAs/Si epilayers was reduced to 3×106 cm-2).The growth of laser materials on Si was researched.The growth conditions of AlGaAs cladding layer and InGaAs/AlGaAs quantum well were optimized.Then,the InGaAs/AlGaAs quantum well laser materials were grown on Si with good crystalline quality and carrier distribution.As shown in TEM images,it can be seen that the threading dislocations were well confined in 1.8-?m-thick GaAs/Si epilayer,and there was almost no dislocation in the quantum well region.(2)We fabricated silicon-based InGaAs/AlGaAs quantum well laser diodes.A threshold current density of 313 A/cm2 has been achieved under pulsed condition at room temperature.It is the lowest threshold current density under pulsed condition among the same type lasers reported.(3)The growth of InAs/GaAs self-assemble QDs on Si was investigated.The size and density of QDs were adjusted by optimizing the growth conditions.After experimental optimization,the density of QDs can reach the order of 1010 cm-2,the QD height is 1.5?4 nm,and the base width is 10?20 nm.Compared with the QDs on GaAs,the QDs on Si are similar in density and size,but its photoluminescence intensity is about 50%of the former.This technique has been applied to the growth of GaAs epilayers on Si in this paper,and has become the basis for the subsequent research of QD lasers.(4)A technique for metamorphic growth of GaAs on(001)oriented Si substrate,with a combination method of applying dislocation filter layer(DFL)and three-step growth process,was proposed.The influence of QD size on the effectiveness of DFL was researched by theoretical calculations.On this basis,the growth conditions of QDs were optimized by experiments.Then,a high-quality GaAs epilayer was grown on the Si substrate with the method including the DFL with InAs QDs and the three-step growth,and its dislocation density was reduced to 9×105 cm-2.(5)A technique for the growth of GaAs epilayers on Si,using the amorphous Si buffer layer and three-step growth method,has been put forward.First,the growth conditions of the amorphous Si buffer layer were optimized.Then,the amorphous Si buffer layer was combined with three-step growth method.The GaAs/Si epilayers with low dislocation density of 1.5×105 cm-2 and good surface morphology were obtained.This result is expected to play an important role in the subsequent research of lasers on Si.