skip to main content

Title: The cross-plane thermoelectric properties of p-Ge/Si{sub 0.5}Ge{sub 0.5} superlattices

The electrical conductivity, Seebeck coefficients, and thermal conductivities of a range of p-type Ge/Si{sub 0.5}Ge{sub 0.5} superlattices designed for thermoelectric generation and grown by low energy plasma enhanced chemical vapor deposition have been measured using a range of microfabricated test structures. For samples with barriers around 0.5 nm in thickness, the measured Seebeck coefficients were comparable to bulk p-SiGe at similar doping levels suggesting the holes see the material as a random bulk alloy rather than a superlattice. The Seebeck coefficients for Ge quantum wells of 2.85 ± 0.85 nm increased up to 533 ± 25 μV/K as the doping was reduced. The thermal conductivities are between 4.5 to 6.0 Wm{sup −1}K{sup −1} which are lower than comparably doped bulk Si{sub 0.3}Ge{sub 0.7} but higher than undoped Si/Ge superlattices. The highest measured figure of merit ZT was 0.080 ± 0.011 obtained for the widest quantum well studied. Analysis suggests that interface roughness is presently limiting the performance and a reduction in the strain between the quantum wells and barriers has the potential to improve the thermoelectric performance.
Authors:
; ; ; ;  [1] ; ; ;  [2] ; ;  [3] ;  [4]
  1. School of Engineering, University of Glasgow, Rankine Building, Oakfield Avenue, Glasgow G12 8LT (United Kingdom)
  2. L-NESS, Politecnico di Milano, Via Anzani 42, 22100 Como (Italy)
  3. Institute of Semiconductor and Solid State Physics, Johannes Kepler Universität, Linz (Austria)
  4. Electron Microscopy ETH Zurich, ETH Zurich, Wolfgang-Pauli-Str. 16, CH-8093 Zurich (Switzerland)
Publication Date:
OSTI Identifier:
22217947
Resource Type:
Journal Article
Resource Relation:
Journal Name: Applied Physics Letters; Journal Volume: 103; Journal Issue: 14; Other Information: (c) 2013 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; 75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; CHEMICAL VAPOR DEPOSITION; DOPED MATERIALS; ELECTRIC CONDUCTIVITY; GERMANIUM; GERMANIUM ALLOYS; GERMANIUM SILICIDES; HOLES; INTERFACES; PERFORMANCE; PLASMA; QUANTUM WELLS; REDUCTION; ROUGHNESS; SEEBECK EFFECT; SEMICONDUCTOR MATERIALS; SILICON ALLOYS; SUPERLATTICES; THERMAL CONDUCTIVITY; THERMOELECTRIC PROPERTIES; THICKNESS