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Science-based Solutions to Achieve High-performance Deep-UV Laser Diodes (Final LDRD Report)

Crawford, Mary H.; Allerman, A.A.; Armstrong, Andrew A.; Miller, Mary A.; Smith, Michael L.; Cross, Karen C.; Lee, Stephen R.; Henry, Tania A.; Alessi, Leonard J.

We present the results of a three year LDRD project that has focused on overcoming major materials roadblocks to achieving AlGaN-based deep-UV laser diodes. We describe our growth approach to achieving AlGaN templates with greater than ten times reduction of threading dislocations which resulted in greater than seven times enhancement of AlGaN quantum well photoluminescence and 15 times increase in electroluminescence from LED test structures. We describe the application of deep-level optical spectroscopy to AlGaN epilayers to quantify deep level energies and densities and further correlate defect properties with AlGaN luminescence efficiency. We further review our development of p-type short period superlattice structures as an approach to mitigate the high acceptor activation energies in AlGaN alloys. Finally, we describe our laser diode fabrication process, highlighting the development of highly vertical and smooth etched laser facets, as well as characterization of resulting laser heterostructures.

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TYPE SAND Report YEAR 2011
DOIOSTI

Smooth and vertical facet formation for AlGaN-based deep-UV laser diodes

Proposed for publication in Applied Physics Letters.

Crawford, Mary H.; Allerman, A.A.; Cross, Karen C.; Shul, Randy J.; Stevens, Jeffrey; Bogart, Katherine H.A.

Using a two-step method of plasma and wet chemical etching, we demonstrate smooth, vertical facets for use in Al{sub x} Ga{sub 1-x} N-based deep-ultraviolet laser-diode heterostructures where x = 0 to 0.5. Optimization of plasma-etching conditions included increasing both temperature and radiofrequency (RF) power to achieve a facet angle of 5 deg from vertical. Subsequent etching in AZ400K developer was investigated to reduce the facet surface roughness and improve facet verticality. The resulting combined processes produced improved facet sidewalls with an average angle of 0.7 deg from vertical and less than 2-nm root-mean-square (RMS) roughness, yielding an estimated reflectivity greater than 95% of that of a perfectly smooth and vertical facet.

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TYPE Journal Article YEAR 2008
OSTI

Final LDRD report : development of advanced UV light emitters and biological agent detection strategies

Crawford, Mary H.; Armstrong, Andrew A.; Allerman, A.A.; Figiel, Jeffrey J.; Schmitt, Randal L.; Serkland, Darwin K.

We present the results of a three year LDRD project which has focused on the development of novel, compact, ultraviolet solid-state sources and fluorescence-based sensing platforms that apply such devices to the sensing of biological and nuclear materials. We describe our development of 270-280 nm AlGaN-based semiconductor UV LEDs with performance suitable for evaluation in biosensor platforms as well as our development efforts towards the realization of a 340 nm AlGaN-based laser diode technology. We further review our sensor development efforts, including evaluation of the efficacy of using modulated LED excitation and phase sensitive detection techniques for fluorescence detection of bio molecules and uranyl-containing compounds.

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TYPE SAND Report YEAR 2007
DOIOSTI
Results 276–300 of 363
Results 276–300 of 363