The Raman and classical Hall effect measurements have been used to determine the longitudinal optical phonon energy, effective mass, and optical phonon relaxation times in Al0.3Ga0.7N/AlN/GaN heterostructures grown by the Molecular Beam Epitaxy (MBE) technique. The classical Hall effect measurements were performed at temperatures between 1.8 and 262 K at a fixed magnetic field, while Raman measurements were performed at room temperature. The longitudinal optical (LO) phonon energy has been found at higher temperatures where Hall mobility data is rapidly decreasing. The effective mass is obtained by comparing the A(1)(LO) peak obtained from Raman measurements to theoretical calculations. The effect of passivation, spacer layer, and doping on the LO phonon relaxation times were determined. The LO phonon relaxation times, which are important for the device's performance, were found between 8.97 and 9.20 fs.