Nonpolar growth and characterization of a-plane InGaN/GaN quantum well structures with different indium compositions

Characteristics of nonpolar (1 1–2 0) a-plane GaN template on r-plane sapphire substrate and subsequently grown InGaN/GaN quantum well (QW) structures were investigated. The crystal orientation and the defect evolution behavior in a-plane GaN template were confirmed by using selected area diffraction and transmittance electron microscopy. The values of full width at half maximum (FWHM) of (1 1–2 0) X-ray rocking curves along the c- and m-directions were 415 and 595 arcsec respectively. The optical characteristics of a-plane InGaN/GaN QW samples with different indium compositions were intensively studied by using temperature-dependent photoluminescence (PL) spectra. The thermal activation energy for localized states increased from 26.5 to 41 meV with increase of indium compositions. Also their relative PL efficiencies and FWHM values showed a potential for nonpolar-based light emitters.