Dresden 2011 – scientific programme

Parts | Days | Selection | Search | Updates | Downloads | Help

HL: Fachverband Halbleiterphysik

HL 69: Nitrides: LEDs

HL 69.2: Talk

Thursday, March 17, 2011, 10:30–10:45, POT 51

Processing of III-nitride thin film light emitting diodes via wafer bonding and laser lift-off — •Christian Goßler, Rüdiger Moser, Michael Kunzer, Klaus Köhler, and Ulrich Schwarz — Fraunhofer-Institut für Angewandte Festkörperphysik, Tullastraße 72, D-9108 Freiburg

High-brightness thin film (Al,In)GaN-based light emitting diodes are generally manufactured by wafer bonding and laser lift-off of the sapphire substrate. This technique is the key for a drastic improvement of light extraction efficiency due to the possibilities of roughening the outcoupling surface and employing a reflective backside contact.

We present the development of a rapid thin film process not using lithographic structuring. A novel bonding scheme based on the eutectic system Aluminium-Germanium is shown. The 2 inch GaN-on-sapphire epiwafers are prepared by depositing 1 µm Aluminium via electron beam evaporation in a shadow mask process. The bonding to a Germanium wafer occurs at high vacuum well above the eutectic temperature of T=693 K. For laser lift-off we use an excimer laser work station emitting at λ=248 nm with a homogenized laser spot of up to 2 mm × 2 mm. Additionally, the GaN layer is separated into mechanically isolated areas prior to wafer bonding by fabricating trenches via picosecond laser processing to improve yield and process control. The thin film LEDs are characterised via electroluminescence and possible effects of the laser trenching are discussed.