The results of experimental studies of the conductivity of AlGaAs/GaAs heterostructure with two-dimensional electron gas at temperatures of 10-300 K are presented. At low temperatures, with a decrease in the distance between the contacts to the structure from 100 to 20 µm, a resistance increase was observed. To explain this anomalous dependence, a numerical simulation of the piezoelectric effect in a semiconductor on the channel conductivity is carried out. It is shown that it is necessary to take into account the crystallographic orientation of the channel and the effect on its potential of remote piezo-charges.