We observed new transport properties in an InGaAs/InAlAs field‐effect transistor with source‐drain separation of ∼40 nm. Through measurements of real‐space transfer current to the gate we obtained clear evidence of ballistic electron transport in the two‐dimensional channel of the device. Another important new feature is the drain current saturation at low drain biases. This effect is explained by a poor electron exchange at the interface of a two‐dimensional gas with bulk at the device contacts.