Uniformity　doping,　delta-doping　and　growth-interruption　doping　to　produce　gallium　nitride　(GaN):　Mg　has　been　investigated　by　low-pressure　metal-organic　chemical　vapor　deposition　(LP-MOCVD).　It　was　demonstrated　by　electrical,　optical,　and　surface　studies　that　films　produced　by　growth-interruption-Mg-doping　produce　the　best　crystal　quality,　this　doping　method　increasing　self-compensation　because　of　the　incorporation　of　additional　impurities　during　the　interruption　period.　Mg-delta-doping　employs　GaN:Mg/UGaN　superlattices　valence　band　edge　oscillation　to　enhance　hole　concentration　leading　to　significantly　reduced　p-type　resistivity,　enhanced　hole　mobility.　This　doping　method　also　leads　to　improved　surface　morphology.　(C)　2007　Published　by　Elsevier　Ltd.