Resonant tunneling through monolayer Si colloidal quantum dots and Ge nanocrystals

Yuanxun Liao*, Pengfei Zhang, Stephen Bramner, Shujuan Huang, Santosh Shrestha, Gavin Conibeer

*Corresponding author for this work

Research output: Contribution to journalArticle

5 Citations (Scopus)

Abstract

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 Al2O3 (a-Al2O3) 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-Al2O3 barriers thinner than the phase coherence length (≈1.5 nm). Ultrathin a-Al2O3 also passivates well materials and suppresses leakage currents. Additionally, the interfacial bandgap of ultrathin a-Al2O3 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.

Original languageEnglish
Article number1605348
Number of pages8
JournalAdvanced Functional Materials
Volume27
Issue number21
DOIs
Publication statusPublished - 6 Jun 2017
Externally publishedYes

Keywords

  • atomic layer deposition
  • Ge nanocrystals
  • Langmuir–Blodgett method
  • resonant tunneling diodes
  • Si quantum dots

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