Full Text Available
Note: Clicking the button above will open the full text document at the original institutional repository in a new window.
Electrical characterization of process, annealing and irradiation induced defects in ZnO
Thesis (PhD)--University of Pretoria, 2013.
Saved in:
| Other Authors: | |
|---|---|
| Format: | Thesis |
| Published: |
University of Pretoria
2013
|
| Subjects: | |
| Tags: |
No Tags, Be the first to tag this record!
|
| _version_ | 1867613641612722176 |
|---|---|
| access_status_str | Open Access |
| author2 | Nel, J.M. |
| author_browse | Nel, J.M. |
| author_facet | Nel, J.M. |
| collection | Thesis |
| dc_rights_str_mv | © 2012 University of Pretoria. All rights reserved. The copyright in this work vests in the University of Pretoria. No part of this work may be reproduced or transmitted in any form or by any means, without the prior written permission of the University of Pretoria. |
| description | Thesis (PhD)--University of Pretoria, 2013. |
| format | Thesis |
| id | oai:repository.up.ac.za:2263/30356 |
| institution | University of Pretoria (South Africa) |
| last_indexed | 2026-06-10T12:39:22.809Z |
| license_str | Other — see source repository |
| provenance_str_mv | Harvested via OAI-PMH from UPSpace — University of Pretoria Institutional Repository |
| publishDate | 2013 |
| publishDateRange | 2013 |
| publishDateSort | 2013 |
| publisher | University of Pretoria |
| publisherStr | University of Pretoria |
| record_format | dspace |
| source_str | UPSpace — University of Pretoria Institutional Repository |
| spelling | oai:repository.up.ac.za:2263/30356 Electrical characterization of process, annealing and irradiation induced defects in ZnO Nel, J.M. Auret, F.D. (Francois Danie) wilbert.mtangi@up.ac.za Mtangi, Wilbert Native defects Schottky barrier height Series resistance Ideality factor Activation enthalpy Irradiation Zno Arrhenius plots Schottky contacts Melt grown Oxygen vacancy Iv Cv Net doping concentration Capture cross-section Dlts Laplace dlts Deep level defects Defects Annealing UCTD Thesis (PhD)--University of Pretoria, 2013. A study of defects in semiconductors is vital as defects tend to influence device operation by modifying their electrical and optoelectronic properties. This influence can at times be desirable in the case of fast switching devices and sometimes undesirable as they may reduce the efficiency of optoelectronic devices. ZnO is a wide bandgap material with a potential for fabricating UV light emitting diodes, lasers and white lighting devices only after the realization of reproducible p-type material. The realization of p-type material is greatly affected by doping asymmetry. The self-compensation behaviour by its native defects has hindered the success in obtaining the p-type material. Hence there is need to understand the electronic properties, formation and annealing-out of these defects for controlled material doping. Space charge spectroscopic techniques are powerful tools for studying the electronic properties of electrically active defects in semiconductors since they can reveal information about the defect “signatures”. In this study, novel Schottky contacts with low leakage currents of the order of 10-11 A at 2.0 V, barrier heights of 0.60 – 0.80 eV and low series resistance, fabricated on hydrogen peroxide treated melt-grown single crystal ZnO samples, were demonstrated. Investigations on the dependence of the Schottky contact parameters on fabrication techniques and different metals were performed. Resistive evaporation proved to produce contacts with lower series resistance, higher barrier heights and low reverse currents compared to the electron-beam deposition technique. Deep level transient spectroscopy (DLTS) and Laplace-DLTS have been employed to study the electronic properties of electrically active deep level defects in ZnO. Results revealed the presence of three prominent deep level defects (E1, E2 and E3) in the as-received ZnO samples. Electron-beam deposited contacts indicated the presence of the E1, E2 and E3 and the introduction of new deep level defects. These induced deep levels have been attributed to stray electrons and ionized particles, present in the deposition system during contact fabrication. Exposure of ZnO to high temperatures induces deep level defects. Annealing samples in the 300°C – 600°C temperature range in Ar + O2 induces the E4 deep level with a very high capture cross-section. This deep level transforms at every annealing temperature. Its instability at room temperature has been demonstrated by a change in the peak temperature position with time. This deep level was broad, indicating that it consists of two or more closely spaced energy levels. Laplace-DLTS was successfully employed to resolve the closely spaced energy levels. Annealing samples at 700°C in Ar and O2 anneals-out E4 and induces the Ex deep level defect with an activation enthalpy of approximately 160 – 180 meV. Vacuum annealing performed in the 400°C – 700°C temperature range did not induce any deep level defects. Since the radiation hardness of ZnO is crucial in space applications, 1.6 MeV proton irradiation was performed. DLTS revealed the introduction of the E4 deep level with an activation enthalpy of approximately 530 meV, which proved to be stable at room temperature and atmospheric pressure since its properties didn’t change over a period of 12 months. Physics unrestricted 2013-09-07T18:52:54Z 2013-04-24 2013-09-07T18:52:54Z 2013-04-17 2013-04-24 2012-12-13 Thesis Mtangi, W 2012, Electrical characterization of process, annealing and irradiation induced defects in ZnO, PhD thesis, University of Pretoria, Pretoria, viewed yymmdd < http://hdl.handle.net/2263/30356 > B13/4/16/ag http://hdl.handle.net/2263/30356 http://upetd.up.ac.za/thesis/available/etd-12132012-162737/ © 2012 University of Pretoria. All rights reserved. The copyright in this work vests in the University of Pretoria. No part of this work may be reproduced or transmitted in any form or by any means, without the prior written permission of the University of Pretoria. application/pdf application/pdf application/pdf application/pdf application/pdf application/pdf application/pdf University of Pretoria |
| spellingShingle | Native defects Schottky barrier height Series resistance Ideality factor Activation enthalpy Irradiation Zno Arrhenius plots Schottky contacts Melt grown Oxygen vacancy Iv Cv Net doping concentration Capture cross-section Dlts Laplace dlts Deep level defects Defects Annealing UCTD Electrical characterization of process, annealing and irradiation induced defects in ZnO |
| title | Electrical characterization of process, annealing and irradiation induced defects in ZnO |
| title_full | Electrical characterization of process, annealing and irradiation induced defects in ZnO |
| title_fullStr | Electrical characterization of process, annealing and irradiation induced defects in ZnO |
| title_full_unstemmed | Electrical characterization of process, annealing and irradiation induced defects in ZnO |
| title_short | Electrical characterization of process, annealing and irradiation induced defects in ZnO |
| title_sort | electrical characterization of process annealing and irradiation induced defects in zno |
| topic | Native defects Schottky barrier height Series resistance Ideality factor Activation enthalpy Irradiation Zno Arrhenius plots Schottky contacts Melt grown Oxygen vacancy Iv Cv Net doping concentration Capture cross-section Dlts Laplace dlts Deep level defects Defects Annealing UCTD |
| url | http://hdl.handle.net/2263/30356 http://upetd.up.ac.za/thesis/available/etd-12132012-162737/ |