Slow interband recombination promotes an anomalous thermoelectric response of the $p-n$ junctions

TL;DR

This paper demonstrates that slow interband recombination in $p-n$ junctions causes anomalous thermoelectric responses, especially when minority carriers' diffusion length exceeds the hot spot size, affecting device performance.

Contribution

It reveals how lack of interband equilibrium leads to unusual thermoelectric voltages, highlighting the importance of interband tunneling in restoring normal behavior.

Findings

Anomalous thermoelectric voltages occur without interband equilibrium.

Slow interband recombination affects thermoelectric response.

Interband tunneling can restore normal thermoelectric behavior.

Abstract

Thermoelectric effects in $p-n$ junctions are widely used for energy generation with thermal gradients, creation of compact Peltier refrigerators and, most recently, for sensitive detection of infrared and terahertz radiation. It is conventionally assumed that electrons and holes creating thermoelectric current are in equilibrium and share the common quasi-Fermi level. We show that lack of interband equilibrium results in an anomalous sign and magnitude of thermoelectric voltage developed across the $p-n$ junction. The anomalies appear provided the diffusion length of minority carriers exceeds the size of hot spot at the junction. Normal magnitude of thermoelectric voltage is partly restored if interband tunneling at the junction is allowed. The predicted effects can be relevant to the cryogenically cooled photodetectors based on bilayer graphene and mercury cadmium telluride quantum wells.