Structural investigation of ultra-low resistance deeply recessed sidewall ohmic contacts for AlGaN/GaN HEMTs based on Ti/Al/Ti-metallization
(2023) In Semiconductor Science and Technology 38(10).- Abstract
This study presents a novel approach to forming low-resistance ohmic contacts for AlGaN/GaN HEMTs. The optimized contacts exhibit an outstanding contact resistance of approximately 0.15 Ω·mm. This is achieved by firstly recessing the barrier of the heterostructure to a depth beyond the channel. In this way, the channel region is exposed on the sidewall of the recess. The coverage of the Ti/Al/Ti ohmic metalization on the sidewall is ensured through tilting of the sample during evaporation. The annealing process is performed at a low temperature of 550 °C. The approach does not require precise control of the recess etching. Furthermore, the method is directly applicable to most barrier designs in terms of thickness and Al-concentration.... (More)
This study presents a novel approach to forming low-resistance ohmic contacts for AlGaN/GaN HEMTs. The optimized contacts exhibit an outstanding contact resistance of approximately 0.15 Ω·mm. This is achieved by firstly recessing the barrier of the heterostructure to a depth beyond the channel. In this way, the channel region is exposed on the sidewall of the recess. The coverage of the Ti/Al/Ti ohmic metalization on the sidewall is ensured through tilting of the sample during evaporation. The annealing process is performed at a low temperature of 550 °C. The approach does not require precise control of the recess etching. Furthermore, the method is directly applicable to most barrier designs in terms of thickness and Al-concentration. The impact of recessed sidewall angle, thickness and ratio of Ti and Al layers, and the annealing procedure are investigated. Structural and chemical analyses of the interface between the ohmic contacts and epi-structure indicate the formation of ohmic contacts by the extraction of nitrogen from the epi-structure. The approach is demonstrated on HEMT-structures with two different barrier designs in terms of Al-concentration and barrier thickness. The study demonstrate large process window in regard to recess depth and duration of the annealing as well as high uniformity of the contact resistance across the samples, rendering the approach highly suitable for industrial production processes.
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- author
- Chen, Ding Yuan ; Persson, Axel R. ; Darakchieva, Vanya LU ; Persson, Per O.Å. ; Chen, Jr Tai and Rorsman, Niklas
- organization
- publishing date
- 2023-10
- type
- Contribution to journal
- publication status
- published
- subject
- keywords
- AlGaN/GaN HEMTs, annealing temperatures, ohmic contact, recessed, sidewall
- in
- Semiconductor Science and Technology
- volume
- 38
- issue
- 10
- article number
- 105006
- publisher
- IOP Publishing
- external identifiers
-
- scopus:85170637812
- ISSN
- 0268-1242
- DOI
- 10.1088/1361-6641/acf396
- language
- English
- LU publication?
- yes
- additional info
- Publisher Copyright: © 2023 IOP Publishing Ltd.
- id
- 4a24a446-ad8d-48b3-85d0-021625634b8e
- date added to LUP
- 2024-01-12 10:11:24
- date last changed
- 2024-02-28 01:11:48
@article{4a24a446-ad8d-48b3-85d0-021625634b8e,
abstract = {{<p>This study presents a novel approach to forming low-resistance ohmic contacts for AlGaN/GaN HEMTs. The optimized contacts exhibit an outstanding contact resistance of approximately 0.15 Ω·mm. This is achieved by firstly recessing the barrier of the heterostructure to a depth beyond the channel. In this way, the channel region is exposed on the sidewall of the recess. The coverage of the Ti/Al/Ti ohmic metalization on the sidewall is ensured through tilting of the sample during evaporation. The annealing process is performed at a low temperature of 550 °C. The approach does not require precise control of the recess etching. Furthermore, the method is directly applicable to most barrier designs in terms of thickness and Al-concentration. The impact of recessed sidewall angle, thickness and ratio of Ti and Al layers, and the annealing procedure are investigated. Structural and chemical analyses of the interface between the ohmic contacts and epi-structure indicate the formation of ohmic contacts by the extraction of nitrogen from the epi-structure. The approach is demonstrated on HEMT-structures with two different barrier designs in terms of Al-concentration and barrier thickness. The study demonstrate large process window in regard to recess depth and duration of the annealing as well as high uniformity of the contact resistance across the samples, rendering the approach highly suitable for industrial production processes.</p>}},
author = {{Chen, Ding Yuan and Persson, Axel R. and Darakchieva, Vanya and Persson, Per O.Å. and Chen, Jr Tai and Rorsman, Niklas}},
issn = {{0268-1242}},
keywords = {{AlGaN/GaN HEMTs; annealing temperatures; ohmic contact; recessed; sidewall}},
language = {{eng}},
number = {{10}},
publisher = {{IOP Publishing}},
series = {{Semiconductor Science and Technology}},
title = {{Structural investigation of ultra-low resistance deeply recessed sidewall ohmic contacts for AlGaN/GaN HEMTs based on Ti/Al/Ti-metallization}},
url = {{http://dx.doi.org/10.1088/1361-6641/acf396}},
doi = {{10.1088/1361-6641/acf396}},
volume = {{38}},
year = {{2023}},
}