Low defect group III nitride films useful for electronic and optoelectronic devices and methods for making the same

Abstract

In a method for making a low-defect single-crystal GaN film, an epitaxial nitride layer is deposited on a substrate. A first GaN layer is grown on the epitaxial nitride layer by HVPE under a growth condition that promotes the formation of pits, wherein after growing the first GaN layer the GaN film surface morphology is rough and pitted. A second GaN layer is grown on the first GaN layer to form a GaN film on the substrate. The second GaN layer is grown by HVPE under a growth condition that promotes filling of the pits, and after growing the second GaN layer the GaN film surface morphology is essentially pit-free. A GaN film having a characteristic dimension of about 2 inches or greater, and a thickness normal ranging from approximately 10 to approximately 250 microns, includes a pit-free surface, the threading dislocation density being less than 1×10⁸ cm⁻².

Description

CROSS-REFERENCE TO RELATED APPLICATIONS [0001] This application claims the benefit of U.S. Provisional Patent Application Ser. No. 60 / 749,728, filed Dec. 12, 2005, titled “Bulk Gallium Nitride Crystals and Method of Making the Same;” U.S. Provisional Patent Application Ser. No. 60 / 750,982, filed Dec. 16, 2005, titled “Method of Producing Freestanding Gallium Nitride by Self-Separation;” U.S. Provisional Patent Application Ser. No. 60 / 810,537, filed Jun. 2, 2006, titled “Low Defect GaN Films Useful for Electronic and Optoelectronic Devices and Method of Making the Same;” U.S. Provisional Patent Application Ser. No. 60 / 843,036, filed Sep. 8, 2006, titled “Methods for Making Inclusion-Free Uniform Semi-Insulating Gallium Nitride Substrate;” and U.S. Provisional Patent Application Ser. No. 60 / 847,855, filed Sep. 28, 2006, titled “Method of Producing Single Crystal Gallium Nitride Substrates by HVPE Method Incorporating a Polycrystalline Layer for Yield Enhancement,” the contents of whic...

AI Technical Summary

Benefits of technology

[0018] According to another implementation, low-defect single-crystal gallium nitride (GaN) on substrate structure is provided. The structure includes a substrate, an epitaxial aluminum nitride (AlN) layer on the substrate, and a GaN film on the substrate. The GaN film includes a first epitaxial GaN growth layer and a second epitaxial GaN growth layer. The first epitaxial GaN layer is grown on the AlN layer under a growth condition that promotes the formation of pits, and after growing the first GaN layer the GaN film surface morphology is rough and pitted. The second epitaxial GaN is grown on the first GaN layer by HVPE under a growth condition that promotes filling of the pits formed, and after growing the second GaN layer the GaN film surface morphology is essentially pit-free.

Problems solved by technology

Most of the III-V nitride devices are grown on foreign substrates such as sapphire (Al2O3) and silicon carbide (SiC) because of the lack of available low-cost, high-quality, large-area native substrates such as GaN substrates.

Because of the lattice mismatch between gallium nitride and the non-native substrate, there is a large number of crystal defects in the GaN film and active device layer.

Despite the high defect density of LEDs grown on these substrates, commercial low-power blue / white LEDs have long lifetimes suitable for some applications.

For LEDs based on an AlGaN active layer operating at the deeper UV range, it is also found that dislocation density has a detrimental effect on the performance and lifetime of the devices.

However, the distribution of the threading dislocation density is not uniform.

The manufacturing cost of the prior-art low defect density GaN film based on MOCVD is high due to multiple growth and photolithographic steps.

The high cost of the film also increases the overall manufacturing cost of end products such as UV LEDs.

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