Werner Goetz

High-brightness AlGaInN light-emitting diodes

Currently, commercial LEDs based on AlGaInN emit light efficiently from the ultraviolet-blue to the green portion of the visible wavelength spectrum. Data are presented on AlGaInN LEDs grown by organometallic vapor phase epitaxy (OMVPE). Designs for high-power AlGaInN LEDs are presented along with their performance in terms of output power and efficiency. Finally, present and potential applications for high-power AlGaInN LEDs, including traffic signals and contour lighting, are discussed.

Material characterization for III-nitride-based light emitters

A review is presented of the electrical and optical properties of nitride based optoelectronic devices, in particular AlGaInN light emitting diodes and laser diode structures. The III-nitride films and devices were grown by organometallic vapor-phase epitaxy on c- and a-face sapphire substrates. We will discuss the structural properties of GaN. InGaN and AlGaN films, heterostructures and InGaN/GaN quantum wells using x-ray diffraction and cross-sectional transmission electron microscope and describe their electrical and optical properties characterized by Hall effect, photoluminescence, and electroluminescence measurements.

Performance and application of high power ultraviolet AlGaInN light emitting diodes

We report on high output power from the quaternary AlGaInN multiple quantum well (MQW) ultraviolet light emitting diodes (UV LEDs) in the 340 nm and 280 nm wavelength range. The output power up to 1.5 mW from a 100 μm diameter device with bare-chip configuration was measured under room temperature cw operation. The internal quantum efficiency was estimated to be between 7 and 10%. In addition, the output power and external quantum efficiency for fully packaged 1x1mm2 large area device were as high as 54.6 mW and 1.45%, respectively, at the injection current of 200 A/cm2 under pulsed operation. The devices were incorporated into prototype system for fluorescence based bio-sensing. We also report the performance of 285 nm UV LEDs.

High-power AlInGaN light-emitting diodes

High-power light-emitting diodes (LEDs) in both the AlInGaP (red to amber) and the AlGaInN (blue-green) material systems are now commercially available. These high-power LEDs enable applications wherein high flux is necessary, opening up new markets that previously required a large number of conventional LEDs. Data are presented on high-power AlGaInN LEDs utilizing flip-chip device structures. The high-power flip-chip LED is contained in a package that provides high current and temperature operation, high reliability, and optimized radiation patterns. These LEDs produce record powers of 350 mW (1A dc, 300 K) with low (<4V) forward voltages. The performance of these LEDs is demonstrated in terms of output power, efficiency, and electrical characteristics.

Characterization of AlGaInN heterostructures and laser diodes

We report on the OMVPE (organometallic vapor phase epitaxial) growth and characterization of AlGaInN heterostructures and laser diodes, including measurements of electrical properties (Hall), structural characteristics (x-ray diffraction and TEM), and room temperature, pulsed laser operation of a 10- quantum well InGaN/AlGaN heterostructure.