Epitaxy of novel AlScN/GaN and AlYN/GaN heterostructures by metal-organic chemical vapour deposition

AlScN and AlYN epitaxial layers bring two advantages for GaN based high-electron mobility transistors (HEMT): The high sheet charge carrier densities in the two-dimensional electron gas at the interface to GaN enables high drain currents and output powers, while the lattice parameter matchings to GaN allows for the growth of strain-free barriers promising for increased lifetimes of devices. For industrial applications, it is essential to grow these materials by metal-organic chemical vapour depostion (MOCVD), but the low vapour pressures of Sc and Y precursors limit the achievable growth rates and the high thermal budget leads to the degradation of the active interfaces.

In this work, the growth rate is increased by employing novel Sc precursors and its impact on the structural and electrical properties of AlScN/GaN heterostructures is investigated in detail. AlScN/GaN HEMTs with the highest reported combination of output power and power added efficiency achieved for class-AB continuous wave operation at Ka-band frequencies on metal-polar GaN-based HEMTs are presented. Growth of AlYN and AlYN/GaN heterostructures by MOCVD is reported and discussed for the first time.