Probing the Thermal and Electrical Properties of Ultrawide Bandgap Nitrogen‐Polar AlGaN Heterostructures

Abstract Ultra‐wide bandgap semiconductor AlGaN is a promising candidate for high‐power and high‐frequency electronics. AlGaN‐heterostructures with nitrogen (N)‐polarity can offer added benefits of low‐leakage and large drive current. However, electro‐thermal transport in such heterostructures remains unexplored, although they are essential for electronic device functionality. Here, the thermal and electrical properties of N‐polar Al x Ga 1‐x N‐channel heterostructures (Al percentage, x = 15–90%) are explored and compared with their GaN counterpart. The thermal measurements uncover that the effective thermal resistance of the thin channel and barrier layers are similar in magnitudes for N‐polar‐ AlGaN and GaN heterostructures, however, the total effective thermal conductivity in N‐polar AlGaN heterostructure is ≈4× smaller. This reduction originates from the larger thermal resistance of the thick Al 0.15 Ga 0.85 N buffer layer within the AlGaN stack. N‐polar Al x Ga 1‐x N stack displays a thermal conductivity almost independent of temperature, measured from room temperature up to 200 °C. Hall measurements of an N‐polar Al 0.30 Ga 0.70 N‐channel heterostructure further reveal that electrical properties such as resistivity, carrier density, and mobility remain nearly unchanged with temperature, indicating the dominance of alloy‐phonon scattering in such material systems. These results offer important insights into material‐device co‐design and reliability of N‐polar AlGaN heterostructures.