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The polarization difference and band offset between Al(Ga)N and GaN induce two-dimensional (2D) free carriers in Al(Ga)N/GaN heterojunctions without any chemical doping. A high-density 2D electron gas (2DEG), analogous to the recently discovered 2D hole gas in a metal-polar structure, is predicted in a N-polar pseudomorphic GaN/Al(Ga)N heterostructure on unstrained AlN. We report the observation of such 2DEGs in N-polar undoped pseudomorphic GaN/AlGaN heterostructures on single-crystal AlN substrates by molecular beam epitaxy. With a high electron density of ∼4.3 [Formula: see text]/cm 2 that maintains down to cryogenic temperatures and a room temperature electron mobility of ∼450 cm 2 /V s, a sheet resistance as low as ∼320 [Formula: see text] is achieved in a structure with an 8 nm GaN layer. These results indicate significant potential of AlN platform for future high-power RF electronics based on N-polar III-nitride high electron mobility transistors.
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PdSe 2 /WSe 2 Nanosheet-Based Heterostructures for n-Type Field-Effect Transistors with Enhanced Performance
Two-dimensional (2D) semiconductors are promising candidates for next-generation flexible electronics, but their performance is often limited by low electron mobility and substantial Schottky barriers (SBs) at metal contacts. Here, we demonstrate that PdSe2/WSe2 nanosheet-based van der Waals heterostructures outperform PdSe2 or WSe2 nanosheets alone as channel materials for n-type field-effect transistors. Here, the WSe2 nanosheet serves as a buffer layer, mitigating Fermi-level pinning and reducing SBs between Ti metal and PdSe2 nanosheets. These heterostructures achieve two-terminal effective mobility exceeding 200 cm2 V–1 s–1 at room temperature and nearing 680 cm2 V–1 s–1 at 77 K. Additionally, the increased bandgap in thinner PdSe2 nanosheets enables high on/off ratios (∼107) in PdSe2/WSe2. These results underscore the potential of PdSe2/WSe2 nanosheet-based heterostructures and the importance of interfacial engineering in advancing 2D electronic devices.
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- Award ID(s):
- 2210861
- PAR ID:
- 10660860
- Publisher / Repository:
- American Chemical Society
- Date Published:
- Journal Name:
- ACS Applied Nano Materials
- Volume:
- 8
- Issue:
- 48
- ISSN:
- 2574-0970
- Page Range / eLocation ID:
- 23130 to 23140
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript
- Journal Article:
- https://doi.org/10.1021/acsanm.5c04263
