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

Abstract

We report on high-quality n-Al0.87Ga0.13N-A0.64Ga0.36N 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 × 103 cm−2. Using reverse composition graded n+-Al x Ga1-xN 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.