Transport properties of lattice-matched AlScN/GaN single- and multichannel heterostructures

Abstract

Lattice-matched aluminum scandium nitride (AlScN) on gallium nitride (GaN) is an attractive material platform for high-power, high-speed GaN electronics. This study investigates the molecular beam epitaxy growth and transport properties of lattice-matched single- and multichannel AlScN/GaN heterostructures. A two-dimensional electron gas (2DEG) forms at the AlScN–GaN interface with a lattice-matched AlScN barrier as thin as 2.5 nm and increases with AlScN thickness, exceeding 2.5 × 1013/cm2 for a 10 nm barrier. Stacking of lattice-matched AlScN/GaN multilayers produces parallel 2DEGs whose total density scales linearly with the number of AlScN/GaN periods, reaching 1 × 1014/cm2 for five-period structures, with moderate average electron mobility of 583 cm2/V.s and sheet resistance of 106 Ω/□ at 300 K. Structural analyses reveal that coherently strained epilayers with sub-nm surface roughness were achieved. The electron mobility in the lattice-matched AlScN/GaN single- and multichannel heterostructures is limited by alloy disorder and interface roughness scattering. Temperature-dependent Hall effect measurements confirm the presence of multiple conducting 2D carrier sheets with less than 15% carrier freeze out, carrier mobility of 851 cm2/V.s, and sheet resistance of 78 Ω/□ at 10 K. Lattice-matched AlScN/GaN multichannel heterostructures can overcome the strain-induced limitations of Al(Ga)N/GaN to deliver GaN-based multilayer structures for RF, power, and photonic devices.