Project

Discipline

nanowires; semiconductor; doping; electronic properties

Lead
Lay summary
Semiconductor nanowires are filamentary crystals with a diameter between a few and ~100 nm. Thanks to their special geometry and dimensions, they constitute one of the most promising building blocks for next generations of electronic and optoelectronic devices.  For this to become a reality, there are some questions to be answered. One of them concerns the controlled introduction of impurities (doping) for the engineering of the electrical properties. While doping in silicon nanowires has achieved a mature understanding, doping of III-V semiconductor nanowires is still an area of intensive research. Indeed, their structure and growth methods exhibit a more complex nature. In this project we address the precise control of the conductivity of nanowires by impurity doping. The nanowires will be synthesized by Molecular Beam Epitaxy (MBE). Our growth method avoids the use of gold as nucleation seed – gold is usually used for nanowire growth. The advantages of our technique are: (i) the possibility of working with ultra-high purity materials and (ii) the wide range of possibilities that MBE offers in terms of sample design for obtaining axial and radial heterostructures. By investigating ultra-high purity nanowires, we will be sure that the measured effects originate from intentional doping and not from spurious effects caused by unwanted impurities (or defects). The project is organized around two main aspects: the synthesis and the investigation of the structural and functional properties. The main techniques that will be used are: Raman Spectroscopy (resonant and non-resonant), High Resolution Transmission Electron Microscopy, cantilever magnetometry and electronic transport as a function of temperature from 300 down to 300 mK . We want to answer the following questions: Is it possible to tune the growth conditions to: (i) avoid doping compensation and (ii) achieve that Si is incorporated mainly as a donor in the nanowire core? How do the doping mechanisms of C and Be on GaAs compare with Si? Is the control of the crystalline phase compatible with doping? Can one design new nanowire (hetero)structures that increase the carrier mobility and doping efficiency? In conclusion, at the end of this project it is our goal to have achieved a fundamental understanding of the doping mechanisms in GaAs nanowires and how heterostructure design can be applied for the improvement of the electronic properties. We expect that the results will be applicable to other synthesis techniques such as Metalorganic Chemical Vapor Deposition and provide a new frame that will offer new perspectives for research on one dimensional structures.

Direct link to Lay Summary

Last update: 21.02.2013

Active participation

Self-organised

Number	Title	Start	Funding scheme

Semiconductor nanowires are filamentary crystals with a diameter between a few and ~100 nm. Thanks to their special geometry and dimensions, they constitute one of the most promising building blocks for next generations of electronic and optoelectronic devices. For this to become a reality, there are some questions to be answered. One of them concerns the controlled introduction of impurities (doping) for the engineering of the electrical properties. While doping in silicon nanowires has achieved a mature understanding, doping of III-V semiconductor nanowires is still an area of intensive research. Indeed, their structure and growth methods exhibit a more complex nature.In this project we address the precise control of the conductivity of nanowires by impurity doping. The nanowires will be synthesized by Molecular Beam Epitaxy (MBE). Our growth method avoids the use of gold as nucleation seed - gold is usually used for nanowire growth. The advantages of our technique are: (i) the possibility of working with ultra-high purity materials and (ii) the wide range of possibilities that MBE offers in terms of sample design for obtaining axial and radial heterostructures. By investigating ultra-high purity nanowires, we will be sure that the measured effects originate from intentional doping and not from spurious effects caused by unwanted impurities (or defects). The project is organized around two main aspects: the synthesis and the investigation of the structural and functional properties. The main techniques that will be used are: Raman Spectroscopy (resonant and non-resonant), High Resolution Transmission Electron Microscopy, cantilever magnetometry and electronic transport as a function of temperature from 300 down to 300 mK . We want to answer the following questions:•Is it possible to tune the growth conditions to: (i) avoid doping compensation and (ii) achieve that Si is incorporated mainly as a donor in the nanowire core?•How do the doping mechanisms of C and Be on GaAs compare with Si? •Is the control of the crystalline phase compatible with doping? •Can one design new nanowire (hetero)structures that increase the carrier mobility and doping efficiency?In conclusion, at the end of this project it is our goal to have achieved a fundamental understanding of the doping mechanisms in GaAs nanowires and how heterostructure design can be applied for the improvement of the electronic properties. We expect that the results will be applicable to other synthesis techniques such as Metalorganic Chemical Vapor Deposition and provide a new frame that will offer new perspectives for research on one dimensional structures.