InGaAs nanowires for high performance electronic devices : growth, characterization and applications
基於砷化銦鎵納米線的高性能電子器件 : 材料生長, 表徵及應用
Student thesis: Doctoral Thesis
Indium Gallium Arsenide (InGaAs) has attracted extensive attention in recent years as a promising material for high-speed and high-frequency electronics devices. However, the one dimensional form of this material is still underdevelopment regarding to the synthesis as well as electrical applications. The uniform ternary InGaAs nanowires with excellent electrical properties and controlled stoichiometry have not been well investigated. In this dissertation, the successful synthesis of ternary stoichiometric InGaAs nanowires with exceptional electrical properties is presented. In addition, the relationship between nanowire diameter and electron field effect mobility has also been investigated. Compared with InAs nanowire based devices, the leakage current in InGaAs nanowire devices could be significantly reduced by raising the electronic band gap. Despite the large scale efforts on utilizing nanowire heterostructures to solve the leakage problem, adopting a uniform ternary InGaAs nanowire as a solution is still lacking. In Chapter 2, we demonstrate the successful synthesis of ternary InGaAs nanowires utilizing the larger band gap material but at the same time not sacrificing the high electron mobility. More importantly, the electrical properties of those nanowires are found to be remarkably impressive. Chapter 3 introduces the large-scale assembly of nanowire parallel arrays by the contact printing method which further illustrates the potency to utilize these high-performance nanowires on substrates for the fabrication of future integrated circuits. Difficulties still exist in synthesis of stoichiometry controllable ternary nanowires, such as crystal quality and uniform diameter distribution. More importantly, the understanding of the relationship between stoichiometry and electrical and optical properties is still lacking to date. In Chapter 4, we present the successful synthesis of composition and band gap tunable InxGa1-xAs alloy nanowires by a simple two−step method. Through manipulating the source powder mixture ratio, we are able to produce stoichiometry ternary InxGa1-xAs NWs with x ranges 0.2-0.75. Moreover, it is found that as the In concentration increases, the band gap energy of NWs falls when the composition shifts towards the Ga−rich while electrical performances such as turn−off and ION/IOFF ratios get improved when the composition shifts towards the Ga-rich end. Chapter 5 details the diameter dependent electron mobility study of InGaAs nanowires grown by gold-catalyzed vapor transport method. The current-voltage behaviors of fabricated nanowire field-effect transistors reveal that the aggressive scaling of nanowire diameter will induce a degradation of electron mobility, while low-temperature measurements further decouple the effects of surface/interface traps and phonon scattering, highlighting the impact of surface roughness scattering on the electron mobility. Chapter 6 discusses the control of the device operation by manipulating the VTH of n-type III-V NWFETs by a metal cluster decoration approach. For the low work function metal clusters (i.e. Al), free carriers are donated from the clusters to the n-type channel such that the VTH is negatively shifted for the D-mode NW transistors, whereas for the high work function metal clusters (i.e. Au), free electrons are withdrawn from the n-type channel to obtain E-mode NW devices. These D- and E-mode devices have also been configured together as logic inverters with excellent performances, which further elucidate the technological potency of this metal cluster decoration for nanoelectronic device fabrication. Finally, Chapter 7 concludes my PhD studies on InGaAs nanowires with respect to two-step growth method, detailed structural characterizations and electrical properties as well as the study of metal decoration method on electrical properties of other III-V nanowires.
- Nanowires, Gallium arsenide semiconductors, Indium arsenide, Electric properties, Semiconductors, Materials