AVS 51st International Symposium
    Science of Semiconductor White Light Topical Conference Wednesday Sessions
       Session WL-WeM

Invited Paper WL-WeM3
Growth of AlGaN-based UV LEDs Emitting at ~280 nm by Metalorganic Chemical Vapor Deposition

Wednesday, November 17, 2004, 9:00 am, Room 304B

Session: Science of Semiconductor White Light I
Presenter: R.D. Dupuis, Georgia Institute of Technology
Authors: R.D. Dupuis, Georgia Institute of Technology
U. Chowdhury, Georgia Institute of Technology
P. Li, Georgia Institute of Technology
J.-H. Ryou, Georgia Institute of Technology
T. Chung, Georgia Institute of Technology
D. Yoo, Georgia Institute of Technology
J.-B. Limb, Georgia Institute of Technology
Correspondent: Click to Email
Wide-bandgap nitride semiconductor materials in the InAlGaN system have attracted attention for deep-ultraviolet (UV) optoelectronic device applications in the spectral range lambda<300nm. In this paper, we report on the status of ternary AlGaN-based UV-LEDs emitting at ~280 nm. These devices are fabricated from epitaxial layers grown using the low-pressure metalorganic chemical vapor deposition (LP-MOCVD) technology. The epitaxial layers are grown on dual-side polished c-plane sapphire substrates and the structure is designed for "flip-chip" operations where light is extracted from the back-side of the substrate. The device structures typically consist of an AlN buffer layer and a low-resistivity n-type Al@sub 0.6@Ga@sub 0.4@N:Si window layer in order improve light extraction while maintaining a low device series resistance and a low spreading resistance. A typical active region consists of three 10nm Al@sub 0.48@Ga@sub 0.52@N:Si barriers with three 5nm Al@sub 0.40@Ga@sub 0.60@N:Si quantum wells. The p-side cladding layer structures generally consist of a 20nm p-type Al@sub 0.52@Ga@sub 0.48@N:Mg electron barrier and a 20nm Al@sub 0.40@Ga@sub 0.60@N:Mg p-type cladding layer (or an AlGaN superlattice cladding layer) while a 25nm GaN:Mg is employed as a p-contact cap layer. We also report on the use of InGaN:Mg p-type layers to reduce the resistance of the p-contact layer in UV LED structures. Due to the lower acceptor ionization energy and lower work function, InGaN:Mg promises or offer better p-layer current spreading and lower contact resistance compared to GaN:Mg. The results of a study of the growth of InGaN:Mg along with Ohmic contact characteristics is described for application to UV-LED structures. The performance of UV LEDs fabricated from these materials will be described.