High figure of merit extreme bandgap Al_0.87Ga_0.13N-Al_0.64Ga_0.36N heterostructures over bulk AlN substrates

Abstract We report on high-quality n -Al 0.87 Ga 0.13 N-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 × 10 3 cm −2 . Using reverse composition graded n + -Al x Ga 1- x N contact layers, we obtained linear ohmic contacts with 4.3 Ω mm specific resistance. A critical breakdown field >11 MV cm −1 was also measured. In combination with the channel resistance of 2400 Ω 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.