AlN/GaN/Sapphire heterostructure for high-temperature packageless acoustic wave devices

•AlN/Sapphire and GaN/Sapphire room-temperature constants sets, which fits our experiments, have been determined.•An AlN/IDT/GaN/Sapphire three layer structure have been simulated, and a WLAW mode is expected. With 12 μm of AlN, this mode is theoretically confined.•The three layer device have been successfully made.•The expected WLAW mode was experimentally measured, and this mode is confined.•The first-order temperature coefficient of elastic constant and expansion coefficients of AlN/Sapphire bilayer structure have been determined. A partial fit for GaN/Sapphire structure have been obtained.•The three layer structure was investigated during temperature in-situ experiments until 500 °C A TCF of −34.6 ppm/°C have been measured.