Buffer-less gallium nitride high electron mobility heterostructures on silicon

Ghosh, Saptarsi, Frentrup, Martin, Hinz, Alexander M, Pomeroy, James W, Field, Daniel, Wallis, David ORCID: https://orcid.org/0000-0002-0475-7583, Kuball, Martin and Oliver, Rachel A 2025. Buffer-less gallium nitride high electron mobility heterostructures on silicon. Advanced Materials , 2413127. 10.1002/adma.202413127

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Abstract

Thick metamorphic buffers are considered indispensable for III-V semiconductor heteroepitaxy on large lattice and thermal-expansion mismatched silicon substrates. However, III-nitride buffers in conventional GaN-on-Si high electron mobility transistors (HEMT) impose a substantial thermal resistance, deteriorating device efficiency and lifetime by throttling heat extraction. To circumvent this, a systematic methodology for the direct growth of GaN after the AlN nucleation layer on six-inch silicon substrates is demonstrated using metal-organic vapor phase epitaxy (MOVPE). Crucial growth-stress modulation to prevent epilayer cracking is achieved even without buffers, and threading dislocation densities comparable to those in buffered structures are realized. The buffer-less design yields a GaN-to-substrate thermal resistance of (11 ± 4) m2 K GW−1, an order of magnitude reduction over conventional GaN-on-Si and one of the lowest on any non-native substrate. As-grown AlGaN/AlN/GaN heterojunctions on this template show a high-quality 2D electron gas (2DEG) whose room-temperature Hall-effect mobility exceeds 2000 cm2 V−1 s−1, rivaling the best-reported values. As further validation, the low-temperature magnetoresistance of this 2DEG shows clear Shubnikov-de-Haas oscillations, a quantum lifetime > 0.180 ps, and tell-tale signatures of spin-splitting. These results could establish a new platform for III-nitrides, potentially enhancing the energy efficiency of power transistors and enabling fundamental investigations into electron dynamics in quasi-2D wide-bandgap systems.

Item Type:	Article
Date Type:	Published Online
Status:	In Press
Schools:	Engineering
Publisher:	Wiley
ISSN:	1521-4095
Date of First Compliant Deposit:	6 January 2025
Date of Acceptance:	31 December 2024
Last Modified:	29 Jan 2025 14:30
URI:	https://orca.cardiff.ac.uk/id/eprint/175019

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