Thermoelectric mapping of p-n junctions and superlattices

An ultra-high-vacuum (UHV) scanning thermoelectric microscopy (SThEM) technique is developed for measuring the Seebeck coefficient profile across individual quantum well and barrier layers of thermoelectric superlattices. The method has been tested on a GaAs p-n junction. and is applied to InGaAs/InGaAsP superlattices. The measured thermoelectric voltage exhibits a sharp transition within a length scale of 2.5 nm, demonstrating the spatial resolution of the SThEM. The measured Seebeck and carrier concentration profiles can be valuable for investigating quantum confinement effects on enhancement of ZT of the quantum well. and for optimizing the growth parameters (thickness and doping) of high ZT superlattices.