Algainn elog led and laser diode structures for pure blue or green emission

US6345063B1 · kind B1 · utility

Assignee

• Xerox Corporation · US

Inventors

• David P. Bour · Cupertino, US
• Linda Romano · Sunnyvale, US
• Michael A. Kneissl · Berlin, DE

Key dates

• Filing date: Jul 28, 1999
• Grant date: Feb 5, 2002
• Expiry date: Jul 28, 2019

Classification

• Technology area (CPC H): Electricity
• CPC primary: H10H20/01335

Abstract

Group III-V nitride semiconductors are used as optoelectronic light emitters. The semiconductor alloy InGaN is used as the active region in nitride laser diodes and LEDs, as its bandgap energy can be tuned by adjusting the alloy composition, to span the entire visible spectrum. InGaN layers of high-indium content, as required for blue or green emission are difficult to grow, however, because the poor lattice mismatch between GaN and InGaN causes alloy segregation. In this situation, the inhomogeneous alloy composition results in spectrally impure emission, and diminished optical gain. To suppress segregation, the high-indium-content InGaN active region may be deposited over a thick InGaN layer, substituted for the more typical GaN. First depositing a thick InGaN layer establishes a larger lattice parameter than that of GaN. Consequently, a high indium content heterostructure active region grown over the thick InGaN layer experiences significantly less lattice mismatch compared to GaN. Therefore, it is less likely to suffer structural degradation due to alloy segregation. Thus, the thick GaN structure enables the growth of a high indium content active region with improved structural…