| EPSRC Reference: |
GR/J16435/01 |
| Title: |
STUDY OF NOVEL HBT STRUCTURES FOR HIGH TEMPERATURE APPLICATIONS |
| Principal Investigator: |
Rezazadeh, Professor AA |
| Other Investigators: |
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| Project Partners: |
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| Department: |
Electronic Engineering |
| Organisation: |
Kings College London |
| Scheme: |
Standard Research (Pre-FEC) |
| Starts: |
01 July 1994 |
Ends: |
30 November 1997 |
Value (£): |
128,486
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| EPSRC Research Topic Classifications: |
| Electronic Devices & Subsys. |
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Summary on Grant Application Form |
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The objective of the project were: (i) To develop a suitable theoretical model for designing novel HBT structures for high-temperature operation.(ii) To investigate ohmic contacts to n- and p-type GaAs which are stable at high-temperature.(iii)To fabricate and determine the practical operating limits of novel HBT structures.Progress:During the past eight months progress has been made in the following areas:(l) The preparation of a dedicated electron beam evaporator for deposition of high-temperature ohmic contacts on GaAs has been completed.(2) A four point probe card with its associated computer programme suitable for data collection and ohmic contact analysis has been designed and is fully operational.(3) The suitability of Ti/Pt/Au metallisation system to high C-doped P-GaAs has been investigated. This contact showed good thermal stability at 300C. High-temperature ohmic contacts to n-GaAs consisting of Ni/Ge/Au with various diffusion barriers have also been studied. In particular the use of ZrB2 as diffusion barrier for emitter and collector contacts to n-p-n HBTs has been investigated. Thermal stress on ohmic contact test samples incorporating ZrB2 barriers showed very little change in specific contact resistance after 100hrs at 300C.(4) A theoretical model based on drift-diffusion has been developed to predict the variation of current gain with temperature for both AlGaAs/GaAs and InGaP/GaAs HBTs. It is shown that base bulk recombination current plays an important role in maintaining the current gain with increasing temperature. In devices where the gain predominantly is determined by emitter/base space-charge recombination the gain had fallen significantly with increasing temperature. Furthermore, it is shown that high C-doped base InGaP/GaAs HBTs are promising devices for operation at high-temperature.Further work is currently in progress to optimise the theoretical model and fabricate various high-temperature HBT structures with particular emphasis on device thermal stability
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Key Findings |
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Potential use in non-academic contexts |
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This information can now be found on Gateway to Research (GtR) http://gtr.rcuk.ac.uk
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Impacts |
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| Description |
This information can now be found on Gateway to Research (GtR) http://gtr.rcuk.ac.uk |
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Sectors submitted by the Researcher |
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This information can now be found on Gateway to Research (GtR) http://gtr.rcuk.ac.uk
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