Phase separation-suppressed and strain-modulated improvement of crystalline quality of AlGaN epitaxial layer grown by MOCVD

Abstract

High crystalline quality AIGaN films were grown on GaN templates by metalorganic chemical vapor deposition (MOCVD). Inhomogeneous distributions of Al compositions in both the vertical and lateral growth direction caused by the strong gas-phase pre-reaction occurring between Al precursors and NH3 were suppressed by optimizing the growth conditions. The residual strain in AIGaN/GaN induced by lattice mismatch, which results in the degradation of crystallinity, was modulated by varying thickness of a high temperature (HT) AIN interlayer (IL) inserted between AIGaN and GaN layers. Both the crystalline quality and Al-incorporation into the AIGaN are influenced by the residual strain related to the AIN IL thickness. Lastly, the understanding of the AIGaN growth and of the strain modification was employed to grow an AIGaN/GaN HEMT structure showing good electrical characteristics and uniformity. (C) 2017 Elsevier Ltd. All rights reserved.