Near-constant thermoelectric power factor of GaN two-dimensional hole gas in cryogenic environments

Abstract

This work investigates the thermoelectric properties of a gallium nitride (GaN)-based two-dimensional hole gas (2DHG) using a double heterojunction, which can be utilized in complementary GaN thermoelectric (TE) platforms for power generation in extreme environments. A 5×1012 cm−2 hole density, a Hall mobility of up to 20 cm2 V−1 s−1, and a Seebeck coefficient of 0.4mVK−1 have been measured, resulting in a power factor of 0.5–1.0mWm−1 K−2 over a 300–77 K temperature range. These results demonstrate the stability and usability of the thermoelectric properties of GaN using hole conduction at sub-100 K temperatures, therefore providing clear evidence that GaN-based 2DHGs can function as a stable cryogenic TE platform, opening new opportunities for complementary device architectures (leveraging both 2DHGs for p-type and two-dimensional electron gases for n-type) optimized for extreme environment electronics commonly encountered in deep-space missions, where other materials become unreliable.