CIPS/OSA Brown Bag Seminar Series

Thursday, April 10, 2008

12 noon , RLE Haus Conference Room 36-428

Lattice Mismatched Epitaxy of Heterostructures for Non-nitride Green Light Emitting Devices

Michael Mori

III-V materials systems for high-brightness light emitting diodes (HBLEDs) and laser diodes (LDs) in the blue and red regions of the visible spectrum are well established, however materials for green emission lag behind in performance. Because of its large bandgap (up to 2.5eV), the quaternary alloy AlInGaP offers promise as a green light emitting material, however lattice-match constraints have traditionally limited it to use at the GaAs lattice constant. More attractive alloys of AlInGaP exist at smaller lattice constants where the direct bandgap is wider with less or no Al and the indirect bandgap is much larger. The greater electrical and optical confinement provided by these materials will shorten wavelength, improve efficiency and enable LDs with record low wavelength. We have focused on AlInGaP alloys with lattice parameters intermediate to GaP and GaAs, at 5.57Å, close to the direct-indirect transition for InGaP.  Fabrication and demonstration of several LEDs emitting amber to green (600-570nm) on the GaAsP platform will be discussed. We will finish with our latest successes in monolithically integrating GaAsP on the Si platform.