Thermal engineering increases current density in AlGaN/GaN superlattice devices

Abstract

Aluminum gallium nitride/gallium nitride multi-channel superlattice devices are receiving increasing attention as a new paradigm for driving the power density of gallium nitride based transistors toward their theoretical limit. However, the superior electrical performance of superlattice-based transistors is currently limited by excessive Joule-heating. This Letter evaluates what impact the number of superlattice channels and the buffer layer composition has on the reduction of the thermal resistance, i.e., Joule heating, of AlGaN/GaN superlattice devices. A record low thermal resistance (12.51 ± 0.34 K mm W−1) was measured via scanning thermal microscopy for non-castellated superlattice AlGaN/GaN devices with a 100 μm channel width. Overall, the use of a thin gallium nitride buffer layer, in place of a thick aluminum gallium nitride layer, reduced the buffer thermal resistance enabling the accommodation of more superlattice channels (10 vs 6), therefore augmenting the maximum power density of these devices. The superlattice device proposed here not only provides an enhanced thermal dissipation solution for high power density radio frequency electronics, but it also has the benefit of fewer fabrication steps in comparison with previously reported castellated multichannel devices.