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

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 AlxGa1-xN-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 approximate to 4x smaller. This reduction originates from the larger thermal resistance of the thick Al0.15Ga0.85N buffer layer within the AlGaN stack. N-polar AlxGa1-xN stack displays a thermal conductivity almost independent of temperature, measured from room temperature up to 200 degrees C. Hall measurements of an N-polar Al0.30Ga0.70N-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. Electro-thermal properties in N-polar AlxGa1-xN-channel heterostructures (x = 15% to 90%) are reported and compared to their GaN counterparts by decoupling the contributions from various sublayers and interfaces. The thermally resistive AlGaN buffer layer predominantly leads to a relatively lower thermal conductivity in AlxGa1-xN heterostructure. The electro-thermal properties of such heterostructures remain nearly unchanged for a wide range of temperatures. image