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Origin(s) of Anomalous Substrate Conduction in MOVPE-Grown GaN HEMTs on Highly Resistive Silicon
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Alexander Hinz ,
Simon M. Fairclough,
Bogdan F. Spiridon,
Abdalla Eblabla,
Michael A. Casbon,
Menno J. Kappers,
Khaled Elgaid,
Saiful Alam,
Rachel A. Oliver ,
David J. Wallis
ACS Applied Electronic Materials, Volume: 3, Issue: 2, Pages: 813 - 824
Swansea University Author:
Saptarsi Ghosh
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DOI (Published version): 10.1021/acsaelm.0c00966
Abstract
The performance of transistors designed specifically for high-frequency applications is critically reliant upon the semi-insulating electrical properties of the substrate. The suspected formation of a conductive path for radio frequency (RF) signals in the highly resistive (HR) silicon substrate its...
| Published in: | ACS Applied Electronic Materials |
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| ISSN: | 2637-6113 2637-6113 |
| Published: |
American Chemical Society (ACS)
2021
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| Online Access: |
Check full text
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| URI: | https://cronfa.swan.ac.uk/Record/cronfa66876 |
| Abstract: |
The performance of transistors designed specifically for high-frequency applications is critically reliant upon the semi-insulating electrical properties of the substrate. The suspected formation of a conductive path for radio frequency (RF) signals in the highly resistive (HR) silicon substrate itself has been long held responsible for the suboptimal efficiency of as-grown GaN high electron mobility transistors (HEMTs) at higher operating frequencies. Here, we reveal that not one but two discrete channels distinguishable by their carrier type, spatial extent, and origin within the metal-organic vapor phase epitaxy (MOVPE) growth process participate in such parasitic substrate conduction. An n-type layer that forms first is uniformly distributed in the substrate, and it has a purely thermal origin. Alongside this, a p-type layer is localized on the substrate side of the AlN/Si interface and is induced by diffusion of group-III element of the metal-organic precursor. Fortunately, maintaining the sheet resistance of this p-type layer to high values (∼2000 Ω/□) seems feasible with particular durations of either organometallic precursor or ammonia gas predose of the Si surface, i.e., the intentional introduction of one chemical precursor just before nucleation. It is proposed that the mechanism behind the control actually relies on the formation of disordered AlSiN between the crystalline AlN nucleation layer and the crystalline silicon substrate. |
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| Keywords: |
GaN-on-Si, GaN HEMTs, AlN nucleation, III-nitride MOVPE, parasitic conduction, RF loss |
| College: |
Faculty of Science and Engineering |
| Funders: |
This research was supported by the Engineering and PhysicalSciences Research Council (EPSRC) under the grantInGaNET, “Integration of RF Circuits with High Speed GaNSwitching on Silicon Substrates” (EP/N017927/1) and (EP/N014820/2). A.H. acknowledges the Deutsche Forschungsge-meinschaft for his Research Fellowship at the University ofCambridge. D.J.W. acknowledges the support of EPSRCfellowship (EP/N01202X/2). The authors are grateful toPlessey Semiconductors Ltd. for performing the Si wafer back-thinning and to Christopher Richards and Robert Harper ofCompound Semiconductor Center Ltd. for performing thecontactless sheet-resistance mapping. S.G. thanks JagannathKuchlyan (Department of Chemistry, University of Oxford)for suggestions on the data analysis. |
| Issue: |
2 |
| Start Page: |
813 |
| End Page: |
824 |