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Resonant Tunneling through Monolayer Si Colloidal Quantum Dots and Ge Nanocrystals
Author(s) -
Liao Yuanxun,
Zhang Pengfei,
Bremner Stephen,
Shrestha Santosh,
Huang Shujuan,
Conibeer Gavin
Publication year - 2017
Publication title -
advanced functional materials
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 6.069
H-Index - 322
eISSN - 1616-3028
pISSN - 1616-301X
DOI - 10.1002/adfm.201605348
Subject(s) - materials science , quantum tunnelling , quantum dot , monolayer , nanocrystal , amorphous solid , resonant tunneling diode , optoelectronics , nanotechnology , diode , band gap , condensed matter physics , quantum well , optics , crystallography , physics , laser , chemistry
Resonant tunneling through a 4 nm nanocrystal Ge (nc‐Ge) layer and a 2.4 nm monolayer of Si colloidal quantum dots (QD) is achieved with 0.7 nm amorphous Al 2 O 3 (a‐Al 2 O 3 ) barriers. The nc‐Ge resonant tunneling diode (RTD) demonstrates a peak‐to‐valley current ratio (PVCR) of 8 and a full width at half maximum (FWHM) of 30 mV at 300 K, the best performance among RTDs based on annealed nanocrystals. The Si QD RTD is first achieved with PVCRs up to 47 and FWHMs as small as 10 mV at room temperature, confirming theoretically expected excellences of 3D carrier confinements. The high performances are partially due to the smooth profile of nc‐Ge layer and the uniform distribution of Si QDs, which reduce the adverse influences of many‐body effects. More importantly, carrier decoherence is avoided in the 0.7 nm a‐Al 2 O 3 barriers thinner than the phase coherence length (≈1.5 nm). Ultrathin a‐Al 2 O 3 also passivates well materials and suppresses leakage currents. Additionally, the interfacial bandgap of ultrathin a‐Al 2 O 3 is found to be similar to the bulk, forming deep potential wells to sharpen transmission curves. This work can be easily extended to other materials, which may enable resonant tunneling in various nanosystems for diverse purposes.