Electrical and luminescent properties of GaN/InGaN multiquantum well light emitting diodes (MQW LEDs) with the top p-GaN layer implanted with 3 x 10(16) cm(-2) Mn ions for potential spin-polarized emission are reported. The forward current in the Mn-implanted diodes was limited by filling of hole traps in the high-resistivity implanted region, the most shallow hole traps having the activation energy of 0.27 eV. Admittance spectroscopy and deep level transient spectroscopy measurements also revealed the presence in the implanted region of traps with apparent activation energies of 0.23, 0.43, 0.5, 0.65 and 0.85 eV. Microcathodoluminescence spectra of the implanted diodes are dominated by two defect bands, the blue band centered near 2.8 eV and the yellow band centered near 2.25 eV, in contrast to the MCL spectra of the virgin diodes dominated by the 2.67 eV band coming from recombination in the GaN/InGaN MQW region. The high resistivity of the implanted region and the high density of deep traps in this region lead to a strong increase in the threshold voltage for the onset of electroluminescence from about 4 V before implantation to about 8 V after implantation. (C) 2003 Elsevier Science Ltd. All rights reserved.