In this work, the hot-electron transport properties of AlInN/AlN/GaN HEMT structures with a high sheet electron density of 4.84x10(13) cm(-2) grown by MOCVD (Metal Organic Chemical Vapor Deposition) on sapphire substrate were investigated at lattice temperature ranging from 10 K to 300 K. High speed current voltage measurements and Hall measurements were used to study hot-electron transport. Current-voltage characteristics show that current and drift velocity increase linearly but deviate from the linearity towards high voltages, as would be expected from the increased scattering of hot electrons with LO phonons. However, no saturation of current and drift velocity were observed at the highest voltage reached. Drift velocities were deduced as approximately 6.7x10(6) and 6.1x10(6) cm/s at an electric field of around E similar to 23 kV/cm at lattice temperatures T-L = 10 K and 300 K, respectively. To obtain the electron temperature as a function of the applied electric field and power loss as a function of the electron temperature, the so-called mobility comparison method with power balance equations were used. The effect of hot-phonon production on the phonon lifetime and effective energy relaxation of hot electrons was investigated as a function of lattice temperature.