Selective Area Epitaxial Growth of Stretchable Geometry AlGaN-GaN Heterostructures
We report on the selective area epitaxy (SAE) of AlGaN/GaN microstructures in stretchable geometric patterns. We have investigated dependence of Al incorporation, lateral/sidewall growth profile and electrical properties of SAE heterostructures on Al/Ga source ratio and mask material. We observe higher Al incorporation along with improvement in heterointerface between the SAE layers with an increase in Al to Ga ratio. AlGaN composition, crystal quality and electrical properties of SAE AlGaN/GaN microstructures are shown to be affected by the choice of mask material. Low resistivity in the range of 0.12–0.35 mΩ cm was measured in these heterostructures. Two terminal current–voltage measurements showed 3–5× higher current density in SAE AlGaN/GaN microstructure devices compared to conventional planar High electron mobility transistor (HEMT). A detailed secondary ion mass spectroscopy (SIMS) profiling on SAE structures showed dependency of unintentional n-type dopants on the mask material.