We designed Mg-doped InGaN/GaN quantum well (QW), strained ultrathin InN/GaN QWs, and Mg and Si delta-doped AlGaN/GaN superlattices (SLs) by using first-principles simulations. The designed structures were grown by metal-organic vapor phase epitaxy (MOVPE) on high-quality thick GaN using an interruption technique. The injection-current-dependent electroluminescence characteristics of Mg-doped QW exhibit smaller injection-current-induced blueshift and energy separation, which indicate that modification of quantized levels has occurred in Mg-cloped QW due to the reduction of polarization field. The cathodoluminescence intensity of the strained ultrathin InN/GaN QWs is enhanced with increasing barrier thickness due to the suppression of interwell coupling, while the emission wavelength redshifts significantly as the well width increases due to reduction of strain in the QW. Higher hole concentration and mobility are achieved in Mg and Si delta-cloped p-type SLs compared to those in modulation-doped SL. These results are in excellent agreement with those of theoretical designs. (C) 2008 Elsevier B.V. All rights reserved.