Design of InGaN/AlInGaN superlattices for white-light device applications S.C.P. Rodrigues a , M.N. d’Eurydice b , G.M. Sipahi b, * , E.F. da Silva Jr. a a Departamento de Fı ´sica, Universidade Federal de Pernambuco, 50670-901 Recife-PE, Brazil b Instituto de Fı ´sica de Sa˜o Carlos, Universidade de Sa˜o Paulo, CP 369, 13560-970 Sa˜o Carlos, SP, Brazil Received 9 March 2005; accepted 19 April 2005 Available online 2 June 2005 Abstract Major developments in wide-gap III–V nitride semiconductors have recently led to the development of LEDs, where the relative intensity of the primary colors in heterostructured diodes can be adjusted to yield white light. Most of the work in III-nitrides, so far, has been done for hexagonal (wurtzite) structures, but research efforts towards a more complete understanding of the cubic (zincblende) nitride-derived heterostructures have increased recently. In particular, with fast and important advances on material processing technology. The AlInGaN quaternary alloy exhibits interesting features, such as higher emission intensity than the ternary AlGaN alloy for certain Al compositions. In addition, it is possible to reach the near ultraviolet (UV) region allowing to better adjustment of white-light emission by mixing different emission wavelengths with adequate intensities. In this work, we perform photoluminescence (PL) and electroluminescence spectra calculations of cubic InGaN/AlInGaN superlattices by using the k$p theory within the framework of the effective mass approximation. The calculations are carried out by solving the 8!8 Kane Hamiltonian. In our calculations, strain effects due to lattice mismatch and the split-off hole band are taken into account. Theoretical PL spectra of these systems are shown and we discuss the effects imposed by Al molar fraction, superlattice composition and structure on the white-light emission properties of the system. q 2005 Elsevier Ltd. All rights reserved. Keywords: Pholuminescence; Eletroluminescence; Nitrides semiconductors 1. Introduction The group III nitride semiconductors including GaN epilayers, InGaN and AlGaN alloys, and InGaN/GaN and AlGaN multiple quantum wells have been intensely studied due to their many applications in ultraviolet (UV)/blue light emitters, solar-blind UV detectors, and high power/ temperature electronic [1]. The devices have been demon- strated in both, the stable hexagonal (h) and cubic (c) phases. Although most of the progress achieved so far is based on the hexagonal materials, the c-metastable phase layers are emerging as promising alternatives for similar applications [2]. Recently, AlInGaN quaternary alloys have been recognized to have the potential to overcome the ternary alloys. Besides, the nitrides quaternary alloys exhibit interesting features as their emission intensities can be higher than the ternary AlGaN and InGaN alloys for certain Al and In compositions. Moreover, it is possible to achieve an extra degree of freedom controlling simultaneously the gap energy and the lattice constant, reducing dislocation density. In addition, the quartenary alloys also have the potential to provide a better thermal match to GaN, which could be an important advantage in epitaxial growth [3]. The significant lack of understanding remains about the exact nature of the optical processes involved in alloys, involving In. Different mechanisms have been proposed for the origin of the carriers’ localized states in the quantum well-based devices. One occurs due to the low solubility of InN in GaN, producing nanoclusters inside the alloy, but can be suppressed by biaxial strain like it was predicted and measured for c-InGaN [1,4,5]. Another proposes that the recombination occurs through the quantum confined states (electron–hole or exciton) inside the well. A short-wavelength UV light of a mercury vapor plasma is commonly used as an exciton source in the majority of commercially available lamps; however, the usage of mercury vapor has been regarded as giving rise to Microelectronics Journal 36 (2005) 1002–1005 www.elsevier.com/locate/mejo 0026-2692/$ - see front matter q 2005 Elsevier Ltd. All rights reserved. doi:10.1016/j.mejo.2005.04.006 * Corresponding author. Tel.: C55 11 3818 6982; fax: C55 11 3818 6984. E-mail address: sipahi@ifsc.usp.br (G.M. Sipahi).