Optimization Of The Optical Properties For InAs/GaAs Semiconductor Quantum Dot Nanomaterials By Incorporating Antimony(Sb)

The InAs/GaAs semiconductor quantum dots?QDs?have unique physical properties to be applied for the development of next-generation optoelectronic devices.The fabrication and characterization of InAs QDs and subsequent the carrier dynamics inside QDs are of great significance for optimizing the performances of versatile optoelectronic devices.In this research,antimony?Sb?is respectively incooperated into the buffer layer surface,the QDs,and the capping layer to modify the optical performances of InAs/GaAs QDs.Spectroscopic mesurements,including photoluminescence?PL?,photoluminescence excitation spectrum?PLE?,and time-resolved photoluminescence spectrum?TRPL?have been used to carefully study the QD emisison and photocarrier dynamics of the above QD nanomaterials.The research includes three sections:?1?The spray of Sb₂ molecular beam on GaAs buffer layer surface has been found to affect the characteristics of InAs QDs.With a slow InAs growth rate of0.013ML/s,the average height of QDs gradually decreases as the Sb₂ spray time increases.The Sb₂ spray of 100 seconds makes InAs QD density increased by nearly an order of magnitude.The PL peak position,intensity,and state-filling behavior of energy levels of QDs after Sb₂ beam spray distinct from that having no Sb₂ spray.In addition,besides QD emission that has the type-I band alignment features,the InAsSb QDs grown on sprayed buffer surface show a type-II PL band at⁹00nm.For the first time such a PL band is interpreted to originate from a GaAs/GaAsSb interface,which is formed as Sb adtoms diffuse from Sb sprayed layer and InAsSb QD layer into the GaAs capping layer.?2?The InAsSb QDs have been investigated after directly adding Sb into QDs.With increasing the Sb₂/?Sb₂+As₂?flux ratio from x=0 to x=0.5,the QDs transit from type I to type II band alignment,while the wetting layer?WL?emission maintains at 850nm with typical type-I characteristics.It is the first experiment for co-exitance of type-I WL with type-II QDs in an InAsSb hybrid QD structure,because the WL and QDs have different Sb composion.In addition to the emission from QDs and WL,a weak PL signal is observed at⁹20 nm after adding Sb into QDs.It originates from GaAs/GaAsSb interface emission with type II band alignment.This emission indicates different mechenism and optical behaviors with increasing the Sb composition.?3?Optical properties were studied for InAs QDs capped by GaAs_1-xSb_x layer of different Sb composition?x=0?0.08?0.11?0.15?0.25?.The QDs with Sb composition x<0.13 in the capping layer show a type-I band alignment,while becoming to type-II with Sb composition x>0.13.These two types of QDs have significantly different characteristics in terms of band filling,carrier thermal activation and recapture behavior,and carrier lifetime.In particular,the type-II QDs reveal new carrier recombination channels.Electrons were controllably doped into the InAs/GaAs_0.85Sb_0.15 type-II QDs.It was found that the doped electrons not only changed the built-in electric field inside the QDs and the band bending caused by Coulomb interaction,but also made the intrinsic transition probability of InAs QDs as well as the Eigen transition probability of GaAsSb QW increasing.The new carrier recombination channel and electron doping effect are otiginal observations.The above research have experimentally testified that by adding Sb we can effectively modify the morphological,structural,and optical properties of InAs QDs.These modified InAs QD nanomaterials have additional recombination channels and enriched carrier dynamics.They not only enable us to understand the basic physical concepts of QDs,but also provide more material choices and experimental basis for the development of next generation of novel opto-electronic devices.