A thermoelectric device (100) includes a pair of spaced apart oppositely doped structures (110, 120) connecting between a common electrode (140) at a first end and different ones of a pair (150) of separate electrodes (150a, 150b) at a second end of the structures. Each oppositely doped structure includes a first material (112, 122) of a respectively doped semiconductor bounded by a second material (114, 124, 116, 126). Boundaries (111, 121) between the respective first and second materials are parallel to a charge carrier conduction path between the common electrode and the separate electrodes. The respectively doped semiconductor has a thickness configured to be less than a phonon scattering length.