The influence of growth pressure on the properties of p-GaN grown by metal-organic chemical vapor deposition method was investigated. The p-GaN layers were grown at low temperature under growth pressures ranging from 100 to 400 mbar. We find that higher growth pressure leads to lower Mg incorporation in the p-GaN layer and results in high resistivity of p-GaN grown at 400 mbar. By optimizing the Cp2Mg/TMGa ratio, however, low sheet resistivity can be achieved for p-GaN grown at 100-300 mbar. The p-GaN grown at 300 mbar using optimal Cp2Mg/TMGa ratio of 1.3% shows the highest hole concentration of 5.0 x 10(17) cm(-3) and the consequent minimum sheet resistivity of 2.6 x 10(4) Omega/sq. The superior electrical properties are ascribed to the reduction of compensation effect for the layer grown under the high growth pressure. (C) 2011 Elsevier B.V. All rights reserved.