Nucleation of Aluminum Nitride on a Silicon Substrate Using an Ammonia Preflow

Abstract

A silicon wafer used in manufacturing crystalline GaN for light emitting diodes (LEDs) includes a silicon substrate, a buffer layer of aluminum nitride (AlN) and an upper layer of GaN. The silicon wafer has a diameter of at least 200 millimeters and an Si(111)1×1 surface. The AlN buffer layer overlies the Si(111) surface. The GaN upper layer is disposed above the buffer layer. Across the entire wafer substantially no aluminum atoms of the AlN are present in a bottom most plane of atoms of the AlN, and across the entire wafer substantially only nitrogen atoms of the AlN are present in the bottom most plane of atoms of the AlN. A method of making the AlN buffer layer includes preflowing a first amount of ammonia equaling less than 0.01% by volume of hydrogen flowing through a chamber before flowing trimethylaluminum and then a subsequent amount of ammonia through the chamber.

Description

TECHNICAL FIELD[0001]The present invention relates generally to methods of growing gallium nitride on silicon.BACKGROUND INFORMATION[0002]Thin films of Group III nitride, such as gallium nitride (GaN), are used in the production of efficient optoelectronic light emitters. Conventionally, GaN has been grown directly on sapphire substrates (Al2O3). The GaN is grown in thin layers as opposed to in a single three-dimensional growth mode in order to achieve a high quality crystalline structure of the epitaxial growth. Growing the epitaxial layers of GaN on silicon as opposed to on sapphire offers considerable cost savings because of the economies of scale from the large production of silicon for the semiconductor industry. A large amount of equipment for the production of crystalline silicon has already been depreciated. That equipment can now be used in the production of light emitting diodes (LEDs).[0003]Current attempts to grow high quality epitaxial layers of GaN on silicon substrate...

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Benefits of technology

The patent text describes a new invention and its technical effects. The details of the invention are explained in the description. The technical effects of the invention are not defined by the summary, but can be inferred from the details described.

Problems solved by technology

Current attempts to grow high quality epitaxial layers of GaN on silicon substrates, however, have not been entirely successful.

Because of the great difference between the lattice constants and thermal expansion coefficients of GaN and silicon, GaN is not well suited for epitaxial growth directly on a silicon substrate.

The quality of the epitaxial GaN layers, however, that can be grown over existing buffer layers has been poor.

Current methods of forming buffer layers of AlN and AlGaN have resulted in epitaxial growth of GaN layers that contain structural defects such as discontinuities, dislocations and faults.

These defects degrade the morphology and optical properties of the GaN layers, rendering the GaN layers unsuitable for use in high quality LEDs.

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