AlGaN/GaN heterostructures in high electron mobility transistors

Abstract

AlGaN/GaN heterostructures are of high research and industrial interest for the production of high electron mobility transistors (HEMT) utilizing the two-dimensional electron gas (2DEG) induced at the interface due to polarization effects. In the current work, the effect of AlGaN thickness on 2DEG formation is under discussion. In particular, ultrathin layers of AlGaN (between 2–12 nm thick) are grown on top of GaN. Composition of these layers is studied and variations of surface potential are mapped using Kelvin probe force microscopy (KPFM) to see the evolution of the 2DEG formation in relation to layer thickness and stoichiometry. The obtained results allow concluding about critical thickness of AlGaN layer for the formation of continuous 2DEG at the AlGaN/GaN interface.