Luminescence Characteristics of N-Polar GaN and InGaN Films Grown by Metal Organic Chemical Vapor Deposition

Abstract

Nitrogen-and Ga-polar GaN and InGaN/GaN multiple quantum-well (MQW) films were prepared via metal organic chemical vapor deposition and evaluated via photoluminescence at reduced temperatures in order to compare their optical characteristics. While N-and Ga-polar GaN films grown at standard high temperatures were comparable in terms of photoluminescence at tested temperatures, the Npolar InGaN MQW quality was inferior to their Ga-polar counterparts, confirmed with greater enhancement in luminescence intensity from 300 to 10 K and unobservable phonon replicas at 10 K for the N-polar InGaN MQW due to the broad emission peak. Additionally performed electroluminescence studies on N-polar light-emitting diode samples indicated that the poor luminescence of the N-polar samples was not related to electric field effects. Influence of residual impurities (C and O) was strongly suggested via secondary ion mass spectroscopy, leading us to conclude that the poor luminescence properties of the N-polar InGaN MQWs were predominantly caused by the elevated residual impurity concentrations in the N-polar (In,Ga)N layers grown at low temperatures. #

Molecular beam epitaxy of N-polar InGaN

“…The FWHM decreases at lower wavelengths which further indicate better optical quality at higher growth temperatures. Our observations are in contrast to the reports by Masui et al 20 where they observe better optical and luminescence qualities for metal-organic chemical vapor deposition grown Ga-face InGaN multiquantum well ͑MQW͒ than N-face InGaN MQW as well as to the reports by Shen et al 21 where they claim superior optical qualities for PAMBE grown Ga-face InGaN over N-face samples.…”

Comparison of the Luminous Efficiencies of Ga- and N-PolarInxGa1−xN/InFernández-Garrido1, Lähnemann2, Hauswald3 et al. 2016Phys. Rev. Applied171140View full textAdd to dashboardCite

“…The poor luminous efficiency of N-polar In x Ga 1−x N QWs does not seem to be a specific problem of PA-MBE, but has also been reported for Npolar In x Ga 1−x N/In y Ga 1−y N QWs grown by metal organic chemical vapor deposition (MOCVD). 3,14,15 Also for the case of MOCVD, this phenomenon is not understood yet, but has been tentatively attributed to higher dislocation densities 14 as well as to elevated residual impurity concentrations. 3,14 In this work, we investigate the luminescence of Gaand N-polar In x Ga 1−x N/In y Ga 1−y N QWs to find a consistent explanation for the differences in their efficiencies.…”

“…3,14,15 Also for the case of MOCVD, this phenomenon is not understood yet, but has been tentatively attributed to higher dislocation densities 14 as well as to elevated residual impurity concentrations. 3,14 In this work, we investigate the luminescence of Gaand N-polar In x Ga 1−x N/In y Ga 1−y N QWs to find a consistent explanation for the differences in their efficiencies. Carrier escape and surface recombination is ruled out by combining simulations of the band profiles with PL measurements carried out with resonant excitation.…”

Investigation on the origin of luminescence quenching in N-polar (In,Ga)N multiple quantum wells

“…This mainly lies in the fact that compared to the metal-polar [0001] direction, growth along the N-polar ½000 1 direction usually yields poorer surface morphology and p-type doping, and higher sensitivity toward impurity incorporation. 6,7 Concerning MBE growth, no direct comparison on the PL of (In,Ga)N MQW structures of both polarities is available. 2,3 More precisely, N-polar green light emitting diodes grown by MBE have also been demonstrated and this result has been made possible by two beneficial effects of the N-polarity.…”