riers R, Arora RC, Tian G. Adipose-derived stem cells are an effective cell candidate for treatment of heart failure: an MR imaging study of rat hearts.

We report on 245–247 nm AlGaN-based deep ultraviolet (DUV) light-emitting diodes with continuous wave output power up to 2 mW. DUV diodes with peak emission wavelength of 245 and 247 nm exhibit turn-on voltage less than 10 V. At room temperature and cw operation the maximum external quantum efficiency was close to 0.18%, which is the highest value published to date for devices with peak emission wavelength shorter than 250 nm. A large external efficiency droop observed at current densities above 100 A/cm2 is attributed to self-heating, carrier spillover from the QWs into the barrier layers or the p-type cladding layer, and/or Auger recombination. A semiempirical equation was proposed to describe the efficiency droop in DUV diodes at a high current injection.

We report on the growth of low-defect thick films of AlN and AlGaN on trenched AlGaN/sapphire templates using migration enhanced lateral epitaxial overgrowth. Incoherent coalescence-related defects were alleviated by controlling the tilt angle of growth fronts and by allowing Al adatoms sufficient residence time to incorporate at the most energetically favorable lattice sites. Deep ultraviolet light emitting diode structures (310nm) deposited over fully coalesced thick AlN films exhibited cw output power of 1.6mW at 50mA current with extrapolated lifetime in excess of 5000hours. The results demonstrate substantial improvement in the device lifetime, primarily due to the reduced density of growth defects.

We report on the development of AlGaN based deep ultraviolet (DUV) light-emitting diodes (LEDs) grown by migration-enhanced metalorganic chemical vapor deposition (MEMOCVD). Improved quality of AlGaN has allowed us to achieve milliwatt-power at wavelengths ranging from 365 to 265 nm. For 295 and 280 nm LEDs, record CW powers with wall-plug-efficiency approaching 1.0% were realized. The CW power reached 1.2 and 1.0 mW at 20 mA for 280 and 295 nm LEDs, respectively. A multiple-chip package (UV lamp) emitted CW power of 11 mW at the wavelength of 280 nm. Under pulse operation, the 280 nm UV lamp produced power as high as 56 mW. The CW power levels at 20 mA were 0.5, 0.25 and 0.15 mW for a single-chip 275, 270 and 265 nm LEDs, respectively. A 265 nm UV lamp exhibited a record high CW power exceeding 1.5 mW. The applications of these DUV LEDs in bio-agents detection have been demonstrated and the preliminary results will be presented.

Optimization of the migration-enhanced metalorganic chemical vapor deposition and further optimization of the contact and active layer design for 280nm light-emitting diodes resulted in large improvement of cw and pulsed output power and in a superior spectrum purity. The ratio of the main peak to the background luminescence determined by the detection system is higher than 2000:1 at 20mA dc. The on-wafer cw power was measured to be 255μW at 20mA dc. The power popped up exceeding 1mW for a packaged device under 25mA dc and 9mW under pulse 200mA. The maximum wall-plug-efficiency of 0.67% was obtained for the packaged device at 25mA dc.