In-plane current through lateral n-i-n junction in GaAs-AlGaAs heterostructure is measured at low temperature. The junction consists of submicron wide narrow wires and an ion damaged insulating region where percolation is a dominant current-carrying mechanism. The current appears at a sufficiently high bias voltage, due to low temperature avalanche breakdown via impurity impact ionization. Time-dependent random-telegraph signals of 100% modulation in magnitude of the current through the i region are observed, which are caused by slow trappings and emissions of electrons at trap sites. The complete switching signals show a transition from normally off to normally on with increasing applied voltage.