The Mg doping behavior of MOVPE indium gallium nitride (InGaN), such as secondary ion mass spectrometry (SIMS) Mg profile, crystalline quality and n-p conversion of the films are described and discussed in this paper. The SIMS analysis reveals that the memory effect of Cp2Mg as a doping source deteriorates the controllability of Mg doping level and profile, especially for thin (-0.4 mu m) InGaN. The high residual donors (10(19)-10(20)cm(-3)) in InGaN with In content from 0.05 to 0.37 can be compensated by Mg doping and p-type conduction is obtained for those with In content up to 0.2. It is found that a higher Cp2Mg flow rate is needed to get p-type conduction in InGaN with a higher In content x; for example, Cp2Mg/(TEG+TMI) approximate to 0.5% for x=0 (GaN), approximate to 2% for x=0.05 and approximate to 4% for x=0.2. Such a high Cp2Mg flow rate is needed due to the high residual donor concentration (10(19)-10(20)cm(-3)) of InGaN films and the low activation efficiency of Mg. The crystalline quality of InGaN is deteriorated with increasing In content as well as Mg doping level. To achieve a p-type InGaN with a lower Mg doping, it is essential to improve the crystalline quality of non-doped InGaN. For this purpose, the use ON thicker GaN interlayer is effective. (C) 2009 Elsevier B.V. All rights reserved.