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    Photonics Materials Topical Conference Thursday Sessions
       Session PH-ThA

Paper PH-ThA4
Development of Integrated Multifunctional Optical Sensors based on III-Nitrides Grown on Si

Thursday, November 1, 2001, 3:00 pm, Room 120

Session: Photonic Materials: Applications and Processing
Presenter: D. Starikov, University of Houston
Authors: D. Starikov, University of Houston
J.-W. Um, University of Houston
C. Boney, University of Houston
A. Bensaoula, University of Houston
Correspondent: Click to Email
An approach to integrating III-Nitrides-based optoelectronic diode structures into multifunctional optical sensors working in the absorption, scattering, or fluorescence mode is described. The proposed concept is evaluated using an optical sensor prototype assembled from discrete III-Nitrides- and Si-based components coupled to a sapphire window. Testing of this prototype proved the applicability of a wide-range silicon photodetector and UV/blue LEDs in multifunctional optical sensors, and the feasibility of the back-side illumination with a lateral setup of the components. Absorption of light was measured in aquatic polyethylene glycol solutions placed between the sapphire window and a mirror attached in front of it. Observable signals were measured for dilutions ranging from 1000-35000 ppm with a linear dependence for concentrations up to 5000 ppm. The internal reflection from the sapphire window, resulted in a low signal-to-noise ratio, since our prototype did not have any antireflection coating. Scattering measurements were performed using slurries of alumina powder in water at particle concentrations from 6x105 to 4x1012 cm-3. The highest sensitivity and dynamic range is achieved for particle sizes of 0.3-5 mm. The photoresponse dependence is linear for very small (0.05 mm) and very large (15 and 20 mm) particles. Fluorescence measurements of Fluoresceinâ„¢ dye and Chlorophyll in ethanol solutions ranging in concentration from 0.029 to 58 ppm show a more than 6 times wider dynamic range and 5000 times higher sensitivity to the concentration variation than either absorption or scattering measurements. In addition fluorescence shows sensitivity to the pH of the solution. The above results are currently utilized in device modeling, simulation and development of integrated GaN-InGaN multifunctional sensors on Si and sapphire. The talk will present the latest results on the growth, processing, and characterization of these sensors.