Effects of UV/O3 or deuterium plasma treatment, of annealing in air at 550°C, of annealing in N2 at 500°C and various combinations of these treatments on leakage current and resistance in the forward direction of GaN/InGaN multiquantum-well light emitting diodes MQW LEDs were studied. It was shown that the best results are achieved with 5 minutes long UV/O3 treatment. LED structures thus prepared showed effects of strong tunneling in their I-V characteristics. The space charge region was shown to be located in the GaN/InGaN superlattice SL. Passing of moderately high forward current through the structure for several hours enhanced the overall tunneling through the structure and facilitated faster tunneling between the layers in the GaN/InGaN SL.