Fabrication and characterization of III-nitride nanophotonic devices

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dc.contributor.author Dahal, Rajendra Prasad
dc.date.accessioned 2009-11-30T17:27:20Z
dc.date.available 2009-11-30T17:27:20Z
dc.date.issued 2009-11-30T17:27:20Z
dc.identifier.uri http://hdl.handle.net/2097/2198
dc.description.abstract III-nitride photonic devices such as photodetectors (PDs), light emitting diode (LEDs), solar cells and optical waveguide amplifiers were designed, fabricated and characterized. High quality AlN epilayers were grown on sapphire and n-SiC substrates by metal organic chemical vapor deposition and utilized as active DUV photonic materials for the demonstration of metal-semiconductor-metal (MSM) detectors, Schottky barrier detectors, and avalanche photodetectors (APDs). AlN DUV PDs exhibited peak responsivity at 200 nm with a very sharp cutoff wavelength at 207 nm and extremely low dark current (<10 fA), very high breakdown voltages, high responsivity, and more than four orders of DUV to UV/visible rejection ratio. AlN Schottky PDs grown on n-SiC substrates exhibited high zero bias responsivity and a thermal energy limited detectivity of about 1.0 x 1015 cm Hz1/2 W-1. The linear mode operation of AlN APDs with the shortest cutoff wavelength (210 nm) and a photocurrent multiplication of 1200 was demonstrated. A linear relationship between device size and breakdown field was observed for AlN APDs. Photovoltaic operation of InGaN solar cells in wavelengths longer than that of previous attainments was demonstrated by utilizing InxGa1−xN/GaN MQWs as the active layer. InxGa1-xN/GaN MQWs solar cells with x =0.3 exhibited open circuit voltage of about 2 V, a fill factor of about 60% and external quantum efficiency of 40% at 420 nm and 10% at 450 nm. The performance of InxGa1-xN/GaN MQWs solar cell was found to be highly correlated with the crystalline quality of the InxGa1-xN active layer. The possible causes of poorer PV characteristics for higher In content in InGaN active layer were explained. Photoluminescence excitation studies of GaN:Er and In0.06Ga0.94N:Er epilayers showed that Er emission intensity at 1.54 µm increases significantly as the excitation energy is tuned from below to above the energy bandgap of these epilayers. Current-injected 1.54 µm LEDs based on heterogeneous integration of Er-doped III-nitride epilayers with III-nitride UV LEDs were demonstrated. Optical waveguide amplifiers based on AlGaN/GaN:Er/AlGaN heterostructures was designed, fabricated, and characterized. The measured optical loss of the devices was ~3.5 cm−1 at 1.54 µm. A relative signal enhancement of about 8 dB/cm under the excitation of a broadband 365 nm nitride LED was achieved. The advantages and possible applications of 1.54 µm emitters and optical amplifiers based on Er doped III-nitrides in optical communications have been discussed. en_US
dc.language.iso en_US en_US
dc.publisher Kansas State University en
dc.subject GaN en_US
dc.subject Photodetector en_US
dc.subject Solar cell en_US
dc.subject Optical amplifier en_US
dc.subject InGaN en_US
dc.subject Erbium en_US
dc.title Fabrication and characterization of III-nitride nanophotonic devices en_US
dc.type Dissertation en_US
dc.description.degree Doctor of Philosophy en_US
dc.description.level Doctoral en_US
dc.description.department Department of Physics en_US
dc.description.advisor Hongxing Jiang en_US
dc.subject.umi Physics, Condensed Matter (0611) en_US
dc.date.published 2009 en_US
dc.date.graduationmonth December en_US

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