Measurements of current-voltage (I-V) characteristics of a high quality Al/Al2O3/Al junction at temperatures ranging from 3.5 K to 300 K have been used to extract the barrier properties. Fitting results using Simmons's model led to a constant value of barrier width s ∼ 20.8 Å and a continuous increase in the barrier height with decreasing temperature. The latter is used to determine the energy band gap temperature dependence and average phonon frequency ω = 2.05 × 1013 s−1 in Al2O3, which adds confidence to the precision of our measurements. The barrier parameters are used to extract the temperature dependent dwell times in tunneling (τD = 3.6 × 10−16 s at mid-barrier energies) and locate resonances above the barrier.