We present measurements of the rates for an electron to tunnel on and off a
quantum dot, obtained using a quantum point contact charge sensor. The tunnel
rates show exponential dependence on drain-source bias and plunger gate
voltages. The tunneling process is shown to be elastic, and a model describing
tunneling in terms of the dot energy relative to the height of the tunnel
barrier quantitatively describes the measurements.Comment: 4 pages, 4 figure