Diamond/β-Ga2O3 pn heterojunction diodes fabricated by low-temperature direct-bonding

Heterojunctions consisting of p-type diamond substrates and thin exfoliated n-type β-Ga2O3 layers were fabricated at a low temperature using a direct-bonding technique. We have fabricated p+-diamond/n-Ga2O3 (p+–n) and p-diamond/n-Ga2O3 (p–n) structures with different B concentrations in diamond. The p+–n heterojunction exhibited Ohmic behavior, resulting from p+-diamond behaving as a metallic layer. As for the p–n heterojunction, it showed clear rectifying action as a conventional bipolar action with a rectifying ratio >108 at ±10 V and leakage current <10−12 A. The ideality factor and barrier height of the p–n heterojunctions were estimated to be 2.7 and 1.5 eV, respectively. Formation of the p–n junction was evidenced by comparing it with the Schottky junction. An energy band diagram of the p–n heterojunctions with staggered (type-II) band alignment was derived based on electrical investigations.