  CrN/MgO(111) multilayers modeled via \textit{ab initio} calculations give
rise to nanoscale, scalable, spatially separated two-dimensional electron and
hole gases (2DEG+2DHG), each confined to its own CrN interface. Due to the Cr
$3d^3$ configuration, both electron and hole gases are based on correlated
transition metal layers involving bands of $3d$ character. Transport
calculations predict each subsystem will have a large thermopower, on the order
of 250 $\mu$$V /K$ at room temperature. These heterostructures combine a large
thermoelectric efficiency with scalable nanoscale conducting sheets; for
example, operating at a temperature difference of 50K, 40 bilayers could
produce a 1 V voltage with a film thickness of 100 nm.
