The successful operation of mid UV LEDs with wavelengths in the range of 250 275 nm and with a marked increase in efficiency and output power relies on the significant reduction in the density of dislocations and V-defects in the MQW; reduction/elimination of spontaneous and piezoelectric polarization in the MQW; significant reduction in stress/strain in the MQW; the identification of the source of UV emission, the reduction of electron overflow from the MQW and significant charge accumulation/recombination only at the upper QWs, enhanced hole concentration in the contact layer; and the development of novel device structures that allow the funneling of carriers into the QWs and low-resistivity contact materials that are transparent to the 250 275 nm UV wavelength range of interest. Finally, UV transparent photonic structures and a UV reflecting layer that is also a p-type contact must be incorporated into flip-chip designs for enhanced wall plug efficiency. An industry/university interdisciplinary team of researchers with synergistic overlap of expertise in growth, multiinstrument characterization and fabrication of AlN substrates, III-Nitride-based LED material structures and LED devices (including UV devices) and prior collaborative experience among the members has been assembled to address these challenges and to meet the stated milestones. Research at ASU will involve detail studies of the microstructure (TEM, XRD), the electronic properties (Electron holography in the TEM) and the optical properties (Cathodoluminescence imaging and time resolved luminescence spectroscopy); all of these carried out at the nanometer scale. A correlation between these properties will lead us to formulate the physics behind crystal growth and device performance.
|Effective start/end date||2/1/12 → 9/30/12|
- DOD-NAVY: Office of Naval Research (ONR): $60,000.00