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Grafted Low-Leakage Si/AlN p-n Diodes Enabled by Fluorinated AlN Interface
Authors:
Yi Lu,
Tsung-Han Tsai,
Qingxiao Wang,
Haicheng Cao,
Jie Zhou,
You Jin Koo,
Chenyu Wang,
Yang Liu,
Yueyue Hao,
Michael Eller,
Connor Bailey,
Stephanie Liu,
Nicholas J. Tanen,
Zhiyuan Liu,
Mingtao Nong,
Robert M. Jacobberger,
Tien Khee Ng,
Katherine Fountaine,
Vincent Gambin,
Boon S. Ooi,
Xiaohang Li,
Zhenqiang Ma
Abstract:
Ultrawide-bandgap AlN is a promising material for next-generation power electronics; however, its practical implementation is hindered by unstable surface chemistry and the high activation energy of p-type dopants. In particular, high-temperature rapid thermal annealing (RTA), required for forming low-resistance contacts on n-type AlN, leads to the formation of thick and defective surface oxides t…
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Ultrawide-bandgap AlN is a promising material for next-generation power electronics; however, its practical implementation is hindered by unstable surface chemistry and the high activation energy of p-type dopants. In particular, high-temperature rapid thermal annealing (RTA), required for forming low-resistance contacts on n-type AlN, leads to the formation of thick and defective surface oxides that degrade heterojunction performance.
In this work, we present an interface engineering approach based on fluorination-induced AlFx formation combined with SiNx passivation to suppress defect-assisted leakage in p-Si/n-AlN heterojunction diodes fabricated via semiconductor grafting. A low-damage pseudo-atomic layer etching process is employed to remove RTA-induced oxides and restore a near-stoichiometric AlN surface. Subsequent XeF2 treatment forms an ultrathin AlFx layer, which is stabilized by an atomic-layer-deposited SiNx capping layer prior to p-Si nanomembrane integration.
Electrical measurements show that the engineered AlFx/SiNx interface reduces reverse leakage current by several orders of magnitude compared to untreated or oxide-removed AlN surfaces, while preserving forward conduction characteristics. Temperature-dependent analysis indicates strong suppression of Poole-Frenkel emission and a shift of leakage onset to higher reverse bias, ultimately limited by bulk AlN crystal quality. X-ray photoelectron spectroscopy and transmission electron microscopy confirm the formation of Al-F bonds, reduced Al-O content, and the presence of a thin interfacial SiOx/SiON layer.
These results establish AlFx/SiNx passivation as an effective strategy for stabilizing AlN interfaces and enabling low-leakage ultrawide-bandgap heterojunction devices.
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Submitted 7 April, 2026;
originally announced April 2026.
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Preliminary Demonstration of Diamond-GaN pn Diodes via Grafting
Authors:
Jie Zhou,
Yi Lu,
Chenyu Wang,
Luke Suter,
Aaron Hardy,
Tien Khee Ng,
Kai Sun,
Yifu Guo,
Yang Liu,
Tsung-Han Tsai,
Xuanyu Zhou,
Connor S Bailey,
Michael Eller,
Stephanie Liu,
Zetian Mi,
Boon S. Ooi,
Matthias Muehle,
Katherine Fountaine,
Vincent Gambin,
Jung-Hun Seo,
Zhenqiang Ma
Abstract:
Ultrawide bandgap (UWBG) semiconductors exhibit exceptional electrical and thermal properties, offering strong potential for high power and high frequency electronics. However, efficient doping in UWBG materials is typically limited to either n type or p type, constraining their application to unipolar devices. The realization of pn junctions through heterogeneous integration of complementary UWBG…
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Ultrawide bandgap (UWBG) semiconductors exhibit exceptional electrical and thermal properties, offering strong potential for high power and high frequency electronics. However, efficient doping in UWBG materials is typically limited to either n type or p type, constraining their application to unipolar devices. The realization of pn junctions through heterogeneous integration of complementary UWBG or WBG semiconductors is hindered by lattice mismatch and thermal expansion differences. Here, we report the preliminary demonstration of diamond GaN heterojunction pn diodes fabricated via grafting. A single crystalline p plus diamond nanomembrane was integrated onto an epitaxially grown c plane n plus GaN substrate with an ultrathin ALD Al2O3 interlayer. The resulting diodes exhibit an ideality factor of 1.55 and a rectification ratio of over 1e4. Structural and interfacial properties were examined by AFM, XRD, Raman, and STEM, providing critical insights to guide further optimization of diamond GaN pn heterojunction devices.
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Submitted 28 October, 2025;
originally announced October 2025.
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Dynamic Versus Static Oxidation of Nb/Al-AlOx/Nb Trilayer
Authors:
Tannaz Farrahi,
Alan W. Kleinsasser,
Michael Cyberey,
Jie Wang,
Micahel B. Eller,
Jian Z. Zhang,
Anthony R. Kerr,
Joseph G. Lambert,
Robert M. Weikle,
Arthur W. Lichtenberger
Abstract:
High quality Nb-based superconductor-insulator-superconductor (SIS) junctions with Al oxide (AlO$_x$) tunnel barriers grown from Al overlayers are widely reported in the literature. However, the thin barriers required for high critical current density (J$_c$) junctions exhibit defects that result in significant subgap leakage current that is detrimental for many applications. High quality, high-J…
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High quality Nb-based superconductor-insulator-superconductor (SIS) junctions with Al oxide (AlO$_x$) tunnel barriers grown from Al overlayers are widely reported in the literature. However, the thin barriers required for high critical current density (J$_c$) junctions exhibit defects that result in significant subgap leakage current that is detrimental for many applications. High quality, high-J$_c$ junctions can be realized with AlN$_x$ barriers, but control of J$_c$ is more difficult than with AlO$_x$. It is therefore of interest to study the growth of thin AlO$_x$ barriers with the ultimate goal of achieving high quality, high-J$_c$ AlO$_x$ junctions. In this work, 100\%\ O$_2$ and 2\%\ O$_2$ in Ar gas mixtures are used both statically and dynamically to grow AlO$_x$ tunnel barriers over a large range of oxygen exposures. In situ ellipsometry is used for the first time to extensively measure AlO$_x$ tunnel barrier growth in real time, revealing a number of unexpected patterns. Finally, a set of test junction wafers was fabricated that exhibited the well-known dependence of J$_c$ on oxygen exposure (E) in order to further validate the experimental setup.
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Submitted 8 September, 2024; v1 submitted 22 June, 2023;
originally announced June 2023.
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Lattice QCD noise reduction for bosonic correlators through blocking
Authors:
Luis Altenkort,
Alexander M. Eller,
O. Kaczmarek,
Lukas Mazur,
Guy D. Moore,
H. -T. Shu
Abstract:
We propose a method to substantially improve the signal-to-noise ratio of lattice correlation functions for bosonic operators or other operator combinations with disconnected contributions. The technique is applicable for correlations between operators on two planes (zero momentum correlators) when the dimension of the plane is larger than the separation between the two planes which are correlated…
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We propose a method to substantially improve the signal-to-noise ratio of lattice correlation functions for bosonic operators or other operator combinations with disconnected contributions. The technique is applicable for correlations between operators on two planes (zero momentum correlators) when the dimension of the plane is larger than the separation between the two planes which are correlated. In this case, the correlation arises primarily from points whose in-plane coordinates are close, but noise arises from all pairs of points. By breaking each plane into bins and computing bin-bin correlations, it is possible to capture these short-distance correlators exactly while replacing (small) correlators at large spatial extent with a fit, with smaller uncertainty than the data. The cost is only marginally larger than averaging each plane before correlating, but the improvement in signal-to-noise can be substantial. We test the method on correlators of the gradient-flowed topological charge density and squared field strength, finding noise reductions by a factor of $\sim$ 3$-$7 compared to the conventional approach on the same ensemble of configurations.
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Submitted 20 May, 2022; v1 submitted 4 December, 2021;
originally announced December 2021.