  It is known that the figure of merit ($ZT$) of thin nanowires can be
significantly enhanced at room temperature due to the reduction of phonon
thermal conductance arising from the increase of boundary scattering of
phonons. It is expected that the phonon thermal conductance of nanowires filled
with quantum dots (QDs) will be further reduced. Here we consider a
superlattice nanowire (SLNW) modeled by a linear chain of strongly coupled QDs
connected to electrodes. We study the dependence of $ZT$ on the QD energy level
($E_0$) (relative to the Fermi level $E_F$ in the electrodes), inter-dot
coupling strength ($t_c$), tunneling rate ($\Gamma$), and temperature $T$ in
order to optimize the design. It is found that at room temperature the maximum
power factor occurs when $(E_0-E_F)/k_BT \approx 2.4$ and $\Gamma=t_c$, a
result almost independent of the number of QDs in SLNW as long as $t_c/k_BT
<0.5$. By using reasonable physical parameters we show that thin SLNW with
cross-sectional width near $3~nm$ has a potential to achieve $ZT\ge3$.
