Review of aluminum nitride buffer layer for high electron mobility transistor applications: growth technique and substrate choice

Purpose This paper aims to highlight the recent trends in growth techniques and substrate utilization for Aluminum Nitride (AlN) as a promising buffer layer in the development of Gallium Nitride (GaN)-based High Electron Mobility Transistors (HEMTs). Design/methodology/approach The review begins with the HEMT structures and the need for an AlN buffer layer, followed by the discussion of the AlN buffer layer related to properties, growth techniques and substrates commonly used. Growth techniques such as metal-organic chemical vapor deposition, atomic layer deposition, molecular beam epitaxy, pulsed laser deposition and magnetron sputtering are discussed. Substrates, including sapphire, silicon carbide and silicon, are also reviewed. Finally, the relationship between growth methods, substrate choice and the resulting AlN buffer layer properties is emphasized. Findings Each growth technique and substrate choice has its own advantages and disadvantages for the resulting AlN buffer properties. While most reported studies remain focused on small wafer sizes (2”–6”), extending AlN growth to larger wafers introduces fundamental challenges related to thermal budget, stress accumulation and wafer-scale uniformity. These constraints become increasingly critical for industrially relevant wafer diameters, particularly on silicon substrates, which highlights the gap between research-scale demonstrations and large-area manufacturing requirements. Originality/value This review provides insights into the current knowledge of AlN buffer layers, focusing on growth techniques and substrate choice. It offers perspectives on the transition from research-scale studies toward cost-effective, large-area AlN buffer layers for GaN-based HEMTs.