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Title: Advances in AlGaN-based deep UV LEDs.

Abstract

Materials studies of high Al-content (> 30%) AlGaN epilayers and the performance of AlGaN-based LEDs with emission wavelengths shorter than 300 nm are reported. N-type AlGaN films with Al compositions greater than 30% reveal a reduction in conductivity with increasing Al composition. The reduction of threading dislocation density from the 1-5 x10{sup 10} cm{sup -2} range to the 6-9 x 10{sup 9}cm{sup -2} range results in an improvement of electrical conductivity and Al{sub 0.90}Ga{sub 0.10}N films with n= 1.6e17 cm-3 and f{acute Y}=20 cm2/Vs have been achieved. The design, fabrication and packaging of flip-chip bonded deep UV LEDs is described. Large area (1 mm x 1 mm) LED structures with interdigitated contacts demonstrate output powers of 2.25 mW at 297 nm and 1.3 mW at 276 nm when operated under DC current. 300 f{acute Y}m x 300 f{acute Y}m LEDs emitting at 295 nm and operated at 20 mA DC have demonstrated less than 50% drop in output power after more than 2400 hours of operation. Optimization of the electron block layer in 274 nm LED structures has enabled a significant reduction in deep level emission bands, and a peak quantum well to deep level ratio of 700:1 has beenmore » achieved for 300 f{acute Y}m x 300 f{acute Y}m LEDs operated at 100 mA DC. Shorter wavelength LED designs are described, and LEDs emitting at 260 nm, 254nm and 237 nm are reported.« less

Authors:
; ; ; ; ; ; ; ;
Publication Date:
Research Org.:
Sandia National Laboratories
Sponsoring Org.:
USDOE
OSTI Identifier:
947341
Report Number(s):
SAND2005-1352C
TRN: US200909%%61
DOE Contract Number:
AC04-94AL85000
Resource Type:
Conference
Resource Relation:
Conference: Proposed for presentation at the 2004 Fall Materials Research Society Meeting held November 29-December 3, 2004 in Boston, MA.
Country of Publication:
United States
Language:
English
Subject:
42 ENGINEERING; 36 MATERIALS SCIENCE; ALUMINIUM NITRIDES; GALLIUM NITRIDES; LIGHT EMITTING DIODES; ULTRAVIOLET RADIATION; TECHNOLOGY ASSESSMENT; PERFORMANCE; DISLOCATIONS; ELECTRIC CONDUCTIVITY; FABRICATION; QUANTUM WELLS; WAVELENGTHS

Citation Formats

Kurtz, Steven Ross, Fischer, Arthur Joseph, Crawford, Mary Hagerott, Ph.D., Wieczorek, Sebastian Maciej, Chow, Weng Wah, Allerman, Andrew Alan, Lee, Stephen Roger, Bogart, Katherine Huderle Andersen, and Kaplar, Robert James. Advances in AlGaN-based deep UV LEDs.. United States: N. p., 2005. Web.
Kurtz, Steven Ross, Fischer, Arthur Joseph, Crawford, Mary Hagerott, Ph.D., Wieczorek, Sebastian Maciej, Chow, Weng Wah, Allerman, Andrew Alan, Lee, Stephen Roger, Bogart, Katherine Huderle Andersen, & Kaplar, Robert James. Advances in AlGaN-based deep UV LEDs.. United States.
Kurtz, Steven Ross, Fischer, Arthur Joseph, Crawford, Mary Hagerott, Ph.D., Wieczorek, Sebastian Maciej, Chow, Weng Wah, Allerman, Andrew Alan, Lee, Stephen Roger, Bogart, Katherine Huderle Andersen, and Kaplar, Robert James. Tue . "Advances in AlGaN-based deep UV LEDs.". United States. doi:.
@article{osti_947341,
title = {Advances in AlGaN-based deep UV LEDs.},
author = {Kurtz, Steven Ross and Fischer, Arthur Joseph and Crawford, Mary Hagerott, Ph.D. and Wieczorek, Sebastian Maciej and Chow, Weng Wah and Allerman, Andrew Alan and Lee, Stephen Roger and Bogart, Katherine Huderle Andersen and Kaplar, Robert James},
abstractNote = {Materials studies of high Al-content (> 30%) AlGaN epilayers and the performance of AlGaN-based LEDs with emission wavelengths shorter than 300 nm are reported. N-type AlGaN films with Al compositions greater than 30% reveal a reduction in conductivity with increasing Al composition. The reduction of threading dislocation density from the 1-5 x10{sup 10} cm{sup -2} range to the 6-9 x 10{sup 9}cm{sup -2} range results in an improvement of electrical conductivity and Al{sub 0.90}Ga{sub 0.10}N films with n= 1.6e17 cm-3 and f{acute Y}=20 cm2/Vs have been achieved. The design, fabrication and packaging of flip-chip bonded deep UV LEDs is described. Large area (1 mm x 1 mm) LED structures with interdigitated contacts demonstrate output powers of 2.25 mW at 297 nm and 1.3 mW at 276 nm when operated under DC current. 300 f{acute Y}m x 300 f{acute Y}m LEDs emitting at 295 nm and operated at 20 mA DC have demonstrated less than 50% drop in output power after more than 2400 hours of operation. Optimization of the electron block layer in 274 nm LED structures has enabled a significant reduction in deep level emission bands, and a peak quantum well to deep level ratio of 700:1 has been achieved for 300 f{acute Y}m x 300 f{acute Y}m LEDs operated at 100 mA DC. Shorter wavelength LED designs are described, and LEDs emitting at 260 nm, 254nm and 237 nm are reported.},
doi = {},
journal = {},
number = ,
volume = ,
place = {United States},
year = {Tue Mar 01 00:00:00 EST 2005},
month = {Tue Mar 01 00:00:00 EST 2005}
}

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  • Current-voltage (IV) characteristics of two AlGaN-based deep ultraviolet (DUV) light-emitting diodes (LEDs) with differing densities of open-core threading dislocations (nanopipes) are analyzed. A three-diode circuit is simulated to emulate the forward-bias IV characteristics of the DUV-LEDs, but is only able to accurately model the lower leakage current, lower nanopipe density DUV-LED. It was found that current leakage through the nanopipes in these structures is rectifying, despite nanopipes being previously established as inherently n-type. Using defect-sensitive etching, the nanopipes are revealed to terminate within the p-type GaN capping layer of the DUV-LEDs. As a result, the circuit model is modified tomore » account for another p-n junction between the n-type nanopipes and the p-type GaN, and an excellent fit to the forward-bias IV characteristics of the leaky DUV-LED is achieved.« less
  • No abstract prepared.
  • An AlGaN Light-emitting diode (LED) emitting with a peak wavelength at 291 nm and a radiant power of 0.5 mW {at} 100 mA was fabricated on a sapphire substrate. A compact gated fluorescence detection system was built using this LED as the excitation light source. We demonstrate that it provides sufficient power using Terbium enhanced fluorescence to detect subnanomolar concentrations of dipicolinic acid (DPA, 2, 6-pyridinedicarboxylic acid), a substance uniquely present in bacterial spores such as that from B. anthracis, providing a basis for convenient early warning detectors. We also describe initial results from a novel approach for biological aerosolmore » detection using long lived fluorescence from a Europium tagged dye that binds to proteins.« less
  • In this paper, the authors overview several of the critical materials growth, design and performance issues for nitride-based UV (< 400 nm) LEDs. The critical issue of optical efficiency is presented through temperature-dependent photoluminescence studies of various UV active regions. These studies demonstrate enhanced optical efficiencies for active regions with In-containing alloys (InGaN, AlInGaN). The authors discuss the trade-off between the challenging growth of high Al containing alloys (AlGaN, AlGaInN), and the need for sufficient carrier confinement in UV heterostructures. Carrier leakage for various composition AlGaN barriers is examined through a calculation of the total unconfined carrier density in themore » quantum well system. They compare the performance of two distinct UV LED structures: GaN/AlGaN quantum well LEDs for {lambda}< 360 nm emission, and InGaN/AlGaInN quantum well LEDs for 370 nm <{lambda}< 390 nm emission.« less
  • The authors overview several of the challenges in achieving high efficiency nitride-based UV (< 400 nm) LEDs. The issue of optical efficiency is presented through temperature-dependent photoluminescence studies of various UV active regions. These studies demonstrate enhanced optical efficiencies for active regions with In-containing alloys (InGaN, AlInGaN). The authors compare the performance of two distinct UV LED structures. GaN/AlGaN quantum well LEDs with {lambda} < 360 nm emission have demonstrated output powers > 0.1 mW, but present designs suffer from internal absorption effects. InGaN/AlInGaN quantum well LEDs with 370 nm < {lambda} < 390 nm emission and > 1 mWmore » output power are also presented.« less