We report on quantum transport in the presence of an electron reflection grating fabricated within a high electron mobility transistor structure. The,orating was composed of a periodically corrugated potential wall by which the electron waves are diffracted. The low temperature conductance shows a number of peaks with respect to the gate voltage, which are consistent with the electron diffraction effect and are predicted by the Fraunhofer diffraction condition. (C) 1997 American Institute of Physics. [S0003-6951(97)01750-6].