Phonon Knudsen flow in GaAs/AlAs superlattices
- Oak Ridge National Lab., TN (United States). Solid State Div.
The measured in-plane thermal conductivity, {delta}{sub SL} of GaAs/AlAs superlattices with even moderate layer thicknesses are significantly smaller than the weighted average, {delta}{sub l} = 67 W/Km, of the bulk GaAs and AlAs conductivities. One expects a suppression of the thermal conductivity to that of an actual Al{sub 0.5}Ga{sub 0.5}As alloy when the thickness of the GaAs and AlAs layers approaches that of a single monolayer. However, the observed superlattice thermal conductivity remains suppressed even at layer thickness {approx_gt} 10 nm. The low thermal conductivities, and very high mobilities, make n-doped GaAs/AlAs superlattices attractive possibilities for thermoelectric devices. With Molecular-Beam-Epitaxial grown GaAs/AlAs superlattices one can expect the individual GaAs and AlAs layers to be extremely clean. Defect and/or alloy scattering is limited to be near the heterostructure interfaces. The authors estimate the room-temperature phonon mean-free-path to be 42 (22) nm for the longitudinal (transverse) mode and thus comparable to or smaller than the layer thicknesses. Thus they expect an important phonon scattering at the interfaces. They study this phonon scattering at the superlattice interfaces assuming a Knudsen flow characterized by diffusive scattering. The solid curve in the figure shows the Knudsen-flow theory estimated for the superlattice thermal conductivity which shows a significant reduction when the layer thickness is shorter than the estimated phonon mean free paths.
- Research Organization:
- Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
- Sponsoring Organization:
- USDOE, Washington, DC (United States)
- DOE Contract Number:
- AC05-84OR21400
- OSTI ID:
- 195692
- Report Number(s):
- CONF-9510111-1; ON: DE96004563; TRN: AHC29605%%68
- Resource Relation:
- Conference: 23. international thermal conductivity conference, Nashville, TN (United States), 29 Oct - 1 Nov 1995; Other Information: PBD: Sep 1995
- Country of Publication:
- United States
- Language:
- English
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