Understanding the growth of III-V semiconductor nanowires with component addition in metal-organic chemical vapor deposition

Abstract

In recent decades, extensive research has been engaged into III-V semiconductor nanowires. It has been widely recognized that they have promising applications for electronic and optoelectronic devices due to their intrinsic material and unique geometry. Currently, the controllable growth of binary III-V nanowires can be achieved via Au-catalysed vapor-liquid-solid method in both metal organic chemical vapor deposition (MOCVD) and molecular beam epitaxy (MBE) system. Conventionally, the key parameters for tuning III-V nanowires’ growths include the growth temperatures, precursor flow rates and the catalyst sizes. However, it has been found that the component addition, i.e. dopants and III/V incorporation, also influenced the controllable growth of III-V nanowires. Therefore, it is meaningful to understand this effect and its underlying influencing mechanism.Doping is a conventional way to introduce impurity atoms into host semiconductor to improve material properties by inducing free electrons or vacancies. The incorporation of impurity atoms can induce electrical property improvement, meanwhile may make the nanowire growth process more complex. However, the effect of doping on nanowire growth is still unclear. In this project, Sn-doped Au-catalysed GaAs nanowires were synthesized in MOCVD with a range of growth parameter including varied growth temperatures and tetraethyl-tin flow rates. The systematic characterizations on as-grown nanowires were carried out by electron microscopy. It was found that the Sn addition influenced the nanowires growth rate and structural quality in different ways at different growth temperatures.Suitable and tuneable bandgaps of ternary III-V nanowires make them suitable for electronic and optoelectronic devices, such as light emission diodes and tandem solar cells. However, elemental segregations have been a long-standing issue in the ternary nanowires, which could induce the core-shell heterostructures in the nanowires. The formation mechanism of core and shell need to be further clarified in order to control the compositional configuration in nanowires, which is meaningful for optimizing their performances in devices. In this project, InGaP nanowires were synthesized in MOCVD and their morphological, structural and compositional characteristics were investigated systematically by electron microscopy. The formation mechanism of the core-shell structure and the axial compositional gradient were discussed. Furthermore, the effect of catalyst size on the growth of hierarchical structured InGaP nanowires was demonstrated.