# The effect of low Al concentration on the electronic structure and thermoelectric properties of AlxGa1−xN/GaN heterojunctions

## TL;DR

This paper studies how small amounts of aluminum affect the electronic and thermoelectric properties of AlxGa1−xN/GaN heterojunctions.

## Contribution

The study reveals specific thermoelectric performance trends at low Al concentrations in AlxGa1−xN/GaN heterojunctions.

## Key findings

- The bandgap increases and the density of states decreases near the Fermi level with higher Al concentration.
- The Al0.25Ga0.75N/GaN heterojunction achieves a Seebeck coefficient of 1850.20 μV/K at 300 K.
- At low Al concentration, the Al0.125Ga0.875N/GaN heterojunction achieves a power factor of 1.48 × 10¹¹ W/(m·K²·s) at 900 K.

## Abstract

The effect of low Al concentrations on the electronic structure and thermoelectric properties of AlxGa1−xN/GaN (x = 0.1250, 0.1875, 0.2500, and 0.3125) heterojunctions was investigated using density functional theory and Boltzmann transport theory. Compared to AlxGa1−xN/GaN heterojunctions with different Al concentrations, it was found that: (1) The bandgap increases and the density of states (DOS) decreases near the Fermi level as the Al concentration increases in AlxGa1−xN/GaN heterojunctions. (2) The Seebeck coefficient of the Al0.25Ga0.75N/GaN heterojunction reaches 1850.20 μV/K at 300 K. (3) For n-type samples, the increase of Al concentration leads to higher conductivity in AlxGa1−xN/GaN heterojunctions. (4) Power factor (PF) decreases with increasing Al concentration in AlxGa1−xN/GaN heterojunctions. At the lowest Al concentration, the power factor of the Al0.125Ga0.875N/GaN heterojunction reaches 1.48 × 1011W/(m·K2·s) at 900K. (5) The maximum electronic thermoelectric quality factor (ZTe) of the Al0.25Ga0.75N/GaN heterojunction reaches 1.41, and at the same temperature, the n-type AlxGa1−xN/GaN heterojunctions exhibit significantly higher performance than the p-type. The results are useful for exploring the thermoelectric properties of GaN-based heterojunctions and improving the performance of thermoelectric devices.