You can freely build on How Nichia Created the First Practical Blue LED Electrodes

What this patent covers

This patent details the construction of a light-emitting diode (LED) using gallium nitride, specifically focusing on how to create reliable electrical connections. It describes a 'second electrode' made of nickel or a nickel-gold alloy that sits on top of the p-type semiconductor layer. To ensure this connection works properly, the patent specifies that the electrode must be annealed—heated to at least 400 degrees Celsius—to form an ohmic contact, which allows electricity to flow easily into the semiconductor. This was critical because, without this specific metal-to-semiconductor interface, the device would not efficiently inject the current required to produce light.

What is now free to use

All 0 claims of US 5563422 are in the public domain. Specifically:

The 0 dependent claims add narrowing limitations and are also free.

What is NOT covered

Patent expiry frees this specific invention. Separately-patented improvements made after expiry may still be protected.

• Does not cover the underlying growth process of the gallium nitride crystal itself.

• Does not cover LEDs made from materials other than gallium nitride-based III-V compounds.

• Does not cover electrode materials that do not utilize nickel or nickel-gold combinations as specified.

• Does not cover non-ohmic contact methods that rely on different electrical physics.

Who is building on this today

Nichia Corporation remains a dominant force in LED manufacturing, continuing to refine the gallium nitride processes established in this era. Major global semiconductor and lighting firms like Cree (now Wolfspeed), Lumileds, and Samsung have all built their LED product lines upon the foundational work of gallium nitride semiconductor devices.

Products built on expired version of this technology

How to cite this patent in your documentation

Nichia Chemical Industries Ltd. US Patent 5563422. Gallium nitride-based III-V group compound semiconductor device and method of producing the same. Granted 1996, expired 2014. Now in the public domain.

Note: This is a convenience citation. Consult a patent attorney for formal freedom-to-operate analysis.

PatentBrief is an educational resource and does not provide legal advice. Patent expiration information is derived from USPTO records and may not reflect continuation patents, divisional filings, or separately-patented improvements. For commercial use or production decisions, obtain a formal freedom-to-operate (FTO) opinion from a registered patent attorney.