Michael Anthony Banas

Low‐temperature study of current and electroluminescence in InGaN/AlGaN/GaN double‐heterostructure blue light‐emitting diodes

Electrical and optical properties of Nichia double‐heterostructure blue light‐emitting diodes, with In0.06Ga0.94N:Zn, Si active layer, are investigated over a wide temperature range from 10 to 300 K. Current–voltage characteristics have complex character and suggest the involvement of various tunneling mechanisms. At small voltages (and currents), the peak wavelength of the optical emission shifts with the applied bias across a large spectral range from 539 nm (2.3 eV) up to 443 nm (2.8 eV). Light emission takes place even at the lowest temperatures, indicating that a complete carrier freeze‐out does not occur.

Metal-Organic Vapor-Phase Epitaxial Growth and Characterization of Quaternary AlGaInN

We report the growth and characterization of quaternary AlGaInN. A combination of photoluminescence (PL), high-resolution X-ray diffraction (XRD), and Rutherford backscattering spectrometry (RBS) characterizations enables us to explore the contours of constant-PL peak energy and lattice parameter as functions of the quaternary compositions. The observation of room temperature PL emission at 351 nm (with 20%Al and 5%In) renders initial evidence that the quaternary could be used to provide confinement for GaInN (and possibly GaN). AlGaInN/GaInN multiple quantum wells (MQWs) heterostructures have been grown; both XRD and PL measurement suggest the possibility of incorporating this quaternary into optoelectronic devices.

Final LDRD Report: Ultraviolet Water Purification Systems for Rural Environments and Mobile Applications

We present the results of a one year LDRD program that has focused on evaluating the use of newly developed deep ultraviolet LEDs in water purification. We describe our development efforts that have produced an LED-based water exposure set-up and enumerate the advances that have been made in deep UV LED performance throughout the project. The results of E. coli inactivation with 270-295 nm LEDs are presented along with an assessment of the potential for applying deep ultraviolet LED-based water purification to mobile point-of-use applications as well as to rural and international environments where the benefits of photovoltaic-powered systems can be realized.

A study of the effect of growth rate and annealing on GaN buffer layers on sapphire

Using atomic force microscopy (AFM) and X-ray diffraction (XRD) the authors have determined that on [0001] oriented sapphire, the GaN buffer layer shows a degree of crystallinity that is dependent on growth rate. Annealing studies show evolution of the crystallinity and the emergence of a preferred orientation. Also, substrate orientation is found to influence the buffer layer crystallinity. Based on this work and previous results, they propose that the GaN buffer layer growth can be described by the Stranski-Krastanov growth process.

MOVPE Growth of Quaternary (Al,Ga,In)N for UV Optoelectronics

We report the growth and characterization of quaternary AlGaInN. A combination of photoluminescence (PL), high-resolution x-ray diffraction (XRD), and Rutherford backscattering spectrometry (RBS) characterizations enables us to explore the contours of constant- PL peak energy and lattice parameter as functions of the quaternary compositions. The observation of room temperature PL emission at 351nm (with 20% Al and 5% In) renders initial evidence that the quaternary could be used to provide confinement for GaInN (and possibly GaN). AlGaInN/GaInN MQW heterostructures have been grown; both XRD and PL measurements suggest the possibility of incorporating this quaternary into optoelectronic devices.

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

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.