Dominik Eisert

Advanced technologies for high-efficiency GaInN LEDs for solid state lighting

Solid state lighting has seen a rapid development over the last decade. They compete and even outperform light sources like incandescent bulbs and halogen lamps. LEDs are used in applications where brightness, power consumption, reliability and costs are key parameters as automotive, mobile and display applications. In the future LEDs will also enter the market of general lighting. For all of these new applications highly efficient, scalable and cost efficient technologies are required. These targets can be matched by SiC based flip chip LEDs which enable the design of high current chips with efficiencies of up to 28 lm/W in white solderable packages. An alternative approach is the implementation of thinfilm technology for GaInN. The LED is fabricated by transferring the epilayers with laser lift off from sapphire to a GaAs host substrate. In combination with efficient surface roughening and highly reflective p-mirror metalization an extraction efficiency of 70% and wall plug efficiency of 24% at 460 nm have been shown. The chips showed 16 mW @ 20 mA with a Voltage of 3.2 V. The technology is scalable from small size LEDs to high current Chips and is being transferred to mass production.

Light extraction technologies for high efficiency GaInN-LED devices

Data are presented for an GaInN based thinfilm LED. The LED is fabricated by transferring the epilayers with laser lift off from sapphire to a GaAs host substrate. In combination with efficient surface roughening and highly reflective p-mirror metallisation an extraction efficiency of 70% and wall plug efficiency of 24% at 460nm have been shown. The chips showed 12mW @ 20mA with a Voltage of 3.2V. The technology is scalable from small size LEDs to high current Chips and is being transferred to mass production.

InGaN on SiC LEDs for high flux and high current applications

We investigate the influence of chip size, substrate shaping and mounting techniques on the light extraction efficiency of large area InGaN-LED chips grown on 6H-SiC substrates. New techniques to achieve good light extraction for large chip areas are demonstrated and discussed. Applying these techniques to InGaN on SiC chips with 1 mm 2 size, we generate 150 mW of blue light and 33 lm of white light at a forward current of 350 mA. For efficient light extraction from the chip and for good thermal coupling the chip is soldered up-side down into a newly developed SMT package with a thermal resistance below 10 K/W.

First European GaN-Based Violet Laser Diode

We report on the realization of room temperature pulsed operation of GaInN multiple quantum well laser diodes. The devices were grown by organometallic vapor phase epitaxy on SiC substrates. Gain guided laser structures with a 8 μm wide resonator show a threshold current density of 17 kA/cm2. For decreasing stripe width the threshold current density increases due to decreasing overlap of electrically pumped area and the lateral extension of the optical wave. The devices were operated at temperatures up to 90 °C with characteristic temperatures of 200 and 290 K for emission wavelengths of 418 and 428 nm, respectively.