| EPSRC Reference: |
GR/M28200/01 |
| Title: |
ELECTRICAL PROPERTIES OF LOW-DIMENSIONAL NITRIDE SEMICONDUCTORS |
| Principal Investigator: |
Harris, Dr J |
| Other Investigators: |
|
| Researcher Co-Investigators: |
|
| Project Partners: |
|
| Department: |
Electronic and Electrical Engineering |
| Organisation: |
UCL |
| Scheme: |
Standard Research (Pre-FEC) |
| Starts: |
01 November 1998 |
Ends: |
31 October 2001 |
Value (£): |
162,028
|
| EPSRC Research Topic Classifications: |
| Materials Characterisation |
|
|
| EPSRC Industrial Sector Classifications: |
| No relevance to Underpinning Sectors |
|
|
| Related Grants: |
|
| Panel History: |
|
|
Summary on Grant Application Form |
|
The purpose of this investigation is to establish the factors which control the electronic properties of low-dimensional structures based on AlGaN/GaInN. This requires the correlation of information from a range of measurement techniques, and the following will be applied to these samples:i) low-field Hall and resistivity measurements from 4.2K to 600K, (ii) current-voltage and capacitance-voltage measurements in the same temperature range, (iii) deep level transient spectroscopy, (iv) low temperature magnetotransport up to 15T, (v) spectroscopic photoconduction measurements from infra-red to bandgap energies, and (vi) velocity-field characteristics as a function of temperature. Information from these measurements will enable optimisation of modulation-doped AlGaN/GaN structures to obtain maximum carrier mobility and saturation velocity over a range of carrier densities, for device and physics applications. These techniques can then be extended to include InGaN channels, in which further improvements in properties can be anticipated both through the reduction in effective mass, and through the use of wavefunction engineering techniques to control 'the spatial distribution of carriers. Finally, an investigation of a 2/0-dimensional system, by the inclusion of self-organised InN quantum dots in the conducting 2DEG channel, and the consequent effects on scattering and trapping, will be undertaken.New AbstractsThe purpose of this investigation was to investigate a number of the factors which influence the electronic properties of low-dimensional structures based on AIGaN/GaN. A basic pre-requisite for this work is an understanding of electronic transport in epitaxial GaN films, and initial studies of a range of samples, using low-field Hall and resistivity measurements from 4.2K to 600K, demonstrated the importance of parallel conduction processes in this material, both at the interface with the substrate, and through impurity bands in the bulk of the material. Similar measurements on AIGaN/GaN 2DEG structures, combined with low temperature magnetotransport studies, demonstrated that such parallel conduction channels are present in the majority of samples studied, and can therefore limit the efficiency of such structures in transistor applications. Access to a particularly high quality AIGaN/GaN 2DEG layer allowed dear magnetotransport data to be obtained for the first time up to 30T, and a detailed analysis of this and related temperature-dependent measurements was undertaken. New results were obtained on (a) the relationship between quantum and transport lifetimes as a function of sample mobility,(b) the energy loss rates of hot electrons, and the phonons involved in this, and (c) the breakdown of the quantum Hall effect in this material system
|
|
Key Findings |
|
This information can now be found on Gateway to Research (GtR) http://gtr.rcuk.ac.uk
|
|
Potential use in non-academic contexts |
|
This information can now be found on Gateway to Research (GtR) http://gtr.rcuk.ac.uk
|
|
Impacts |
|
| Description |
This information can now be found on Gateway to Research (GtR) http://gtr.rcuk.ac.uk |
| Summary |
|
| Date Materialised |
|
|
|
|
Sectors submitted by the Researcher |
|
This information can now be found on Gateway to Research (GtR) http://gtr.rcuk.ac.uk
|
| Project URL: |
|
| Further Information: |
|
| Organisation Website: |
|