Abstract
In this paper, optimizations of thermoelectric(TE) properties for the rough surface of the nano-ridge GaAs/AlAs superlattice(SL) structure are investigated. The nano-ridge featured with rough surface at both sides of the SL structure is introduced, where the modification of the phonon spatial confinement and phonon surface roughness scattering are taken into account. The elastic continuum model is employed to calculate the phonon dispersion relation and the related phonon group velocity. Reported experimental results with SL structures were used for verification of our model. The lattice thermal conductivity, electrical conductivity, Seebeck coefficient, and electronic thermal conductivity are calculated by Boltzmann transport equations and relaxation time approximation. Simulation results show that the nano-ridge SL structure with certain periodicity and phonon surface roughness scattering have strong influences on the TE properties. Highest ZT in our calculation is 1.285 at 300K and the ZT value of 3.04 is obtained at 1000K.
Highlights
The energy crisis is imminent and to find efficient power conversion solutions becomes an urgent work in recent years
Note that the surface fermi level pinning effect at the air/SL surface, the electrons are mainly accumulated at the center of the nano-ridge SL structure so that the surface roughness scattering of electrons could be neglected
The lowest lattice thermal conductivity in our proposed rough surface of the nano-ridge GaAs/AlAs SL structure is kph=0.10W/mK and the surface roughness is described by the auto-covariance length L=6.0nm[50] and the roughness degree RMS ∆=1.5nm
Summary
The energy crisis is imminent and to find efficient power conversion solutions becomes an urgent work in recent years. In 1999, Capinski et al.[35] utilized experimentally a picosecond optical pump-and-probe technique to measure the cross-plane lattice thermal conductivity of the GaAs/AlAs SL structures for the temperature dependence on different SL structure layer thicknesses. Since Capinski published their measurements, theoretical models[33,37,40,41,42] were applied to this experimental results.[35] To further reduce the thermal conductivity for TE applications, it would be good to apply the rough side wall surface to enhance the surface boundary scattering This can be done by applying a nano-ridge structure. The elastic continuum model and finite difference(FD) method are adapted to calculate the phonon dispersion relation Both BTE and relaxation time approximation(RTA) are applied in our proposed nano-ridge SL structures to obtain the phonon lattice thermal conductivity, electrical conductivity, Seebeck coefficient, and electronic thermal conductivity.
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
