Two-dimensional electron gases induced by polarization charges in AlN/GaN heterostructure grown by plasma-assisted molecular-beam epitaxy

Abstract

We discuss the growth and transport properties of two-dimensional electron gas confined at the AlN/GaN heterointerface grown by plasma-assisted molecular-beam epitaxy. The sheet carrier density was found to be highly dependent on the barrier thickness of AlN grown on a doped or undoped GaN layer. The carrier sheet density monotonously increased from 0.8×1012 to 1.1×1013 cm−2 as the AlN barrier thickness on a semi-insulating GaN layer increased from 15 to 25 Å due to spontaneous and piezoelectric polarization. An AlN barrier of 35 Å in thickness grown on n-GaN gave the highest sheet carrier density, which was 4.3×1013 cm−2. In thin AlN barrier layers, the sheet carrier density was low due to surface depletion.