Lattice-constant formatted epitaxial template for light emitting devices and a method for making the same

Abstract

A lattice constant formatted epitaxial template for light emitting devices includes a starting epitaxial template having a base, a plurality of alternately arranged protrusions and depressions on the base; first material portions epitaxially formed on top of the protrusions and second material portions epitaxially formed in the depressions, wherein lattice constants of the first material portions on the protrusions are different from those of the second material portions in the depressions. A method for making a lattice constant formatted epitaxial template is provided. Also provided is a light emitting device containing a lattice constant formatted epitaxial template.

Description

FIELD OF THE INVENTION[0001]The present invention relates in general to a lattice-constant formatted epitaxial template for semiconductor light emitters, more particularly for group III nitride compound semiconductor ultraviolet light or visible light emitters, a method of forming the same, and a light emitting device containing a lattice constant formatted epitaxial template.1. DESCRIPTION OF THE RELATED ART[0002]Nitride compound semiconductors such as InN, GaN, AlN, and their ternary and quaternary alloys are viewed as very important optoelectronic materials. Depending on alloy composition, nitride compounds can enable ultraviolet (UV) emissions ranging from 410 nm down to approximately 200 nm. This includes UVA (400-315 nm), UVB (315-280 nm), and part of UVC (280-200 nm) regimes. UVA emissions are leading to revolutions in curing industry, and UVB and UVC emissions owing to their germicidal effect are looking forward to general adoption in food, water, and surface disinfection bu...

AI Technical Summary

Benefits of technology

The present invention relates to a light emitting device that includes a lattice constant formatted epitaxial template. The template has alternating first and second material portions with different lattice constants. The device also includes an n-type layer, a p-type layer, and an active region sandwiched between them. The active region is directly formed on the first and second material portions of the template. The invention also provides a method for making the lattice constant formatted epitaxial template by simultaneously growing first and second material portions on protrusions and depressions on a starting epitaxial template. The device and method have improved efficiency and stability.

Problems solved by technology

Prior art UV LEDs suffer from low light output efficiency.

Firstly, there is no lattice matched substrate for AlGaN based devices, which means strain management is essential for AlGaN device performance.

Thick AlN template or bulk AlN substrate exerts large biaxial compression on the overlying AlGaN based device structure, resulting in additional dislocation generation and surface roughness leading to inferior device performance.

Biaxial tensile strain not only generates dislocations to deteriorate device internal quantum efficiency but also lead to surface cracks which are deadly device defects.

The other drawback of the prior art UV LEDs comes from light extraction, since the employment of UV absorbing p-GaN or p-InGaN contact layer and the large differences in the refractive indexes among air, sapphire, AlN, and AlGaN make light extraction out of the solid state device marginal, usually limiting light extraction efficiency to as small as 6%-10%.

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