High figure of merit extreme bandgap Al0.87Ga0.13N-Al0.64Ga0.36N heterostructures over bulk AlN substrates

We report on high-quality n-Al0.87Ga0.13N-A(0.64)Ga(0.36)N heterostructures over single crystal AlN. For these pseudomorphic heterostructures, high-resolution X-ray and X-ray Topographic analysis was used to establish a threading dislocation density of 7 x 10(3) cm(-2). Using reverse composition graded n(+)-Al (x) Ga1-x N contact layers, we obtained linear ohmic contacts with 4.3 omega mm specific resistance. A critical breakdown field >11 MV cm(-1) was also measured. In combination with the channel resistance of 2400 omega sq(-1), these translate to a Baliga's Figure of Merit of 2.27 GW cm(-2). This, to the best of our knowledge is the highest reported value for extreme bandgap AlGaN heterostructures.