1992 Nichia Chemical Industries researchers Shuji Nakamura / Takashi Mukai / Naruhito Iwasa co-filed US5578839A 'Light-emitting gallium nitride-based compound semiconductor device'—the InGaN double-heterostructure blue LED core patent. Original Assignee Nichia Chemical Industries Ltd (DB correction: pre-2003 company name; current Nichia Corporation is the Current Assignee). The DB entry 'Shuji Nakamura solo' is also corrected. 22nd correction in the Day 8–18 sequence

About excavation memos: "Excavation memos" in this series record candidate summaries at the stage where the primary URL has been confirmed. This memo retrieves the Claim 1, three inventors (Nakamura, Mukai, Iwasa), filing/grant dates, assignees (Nichia Chemical Industries Ltd → Nichia Corporation), and title from Google Patents, but the full specification (InGaN crystal growth conditions, p-type GaN doping technical details, relationship to the 1989 Akasaki/Amano p-type GaN paper) is unread. Only confirmed facts are stated; speculation is marked as such.

Why excavate this

Blue LEDs provide the material foundation for all modern (a) white-LED lighting (residential, office, data center), (b) liquid-crystal TV / monitor / laptop backlight light sources, (c) smartphone backlights, (d) Mini-LED TVs (Samsung, LG, TCL, Hisense), (e) Micro-LED display research, (f) Blu-ray Disc / laser-printer violet lasers, and (g) GaN-based power semiconductors (EV inverters, data-center power supplies). The starting point was November 29, 1993, when Nichia Chemical Industries achieved the world's first mass production of high-brightness InGaN blue LEDs; the US patent covering the core invention is US5578839A, the subject of this memo.

The excavation establishes via primary sources that, as the title indicates ("Light-emitting gallium nitride-based compound semiconductor device"), this patent is the core patent for GaN-based double-heterostructure light-emitting devices, and that the material foundation of modern white-LED lighting / LCD backlights / Mini-LED TVs traces back to this 1992 filing. It creates the starting point of the display side of haruko's main niche (Chinese AI × Korean/Taiwanese semiconductors × robotics translation).

Patent basic information

• Patent number: US5578839A
• Title: Light-emitting gallium nitride-based compound semiconductor device
• Inventors: Shuji Nakamura, Takashi Mukai, Naruhito Iwasa — three co-inventors
• Original Assignee: Nichia Chemical Industries Ltd (then-current company name; HQ in Anan, Tokushima)
• Current Assignee: Nichia Corporation (after the 2003 name change)
• Priority Date: 1992-11-20 (Japan)
• Filing Date: 1993-11-17 (US continuation)
• Grant Date: 1996-11-26
• Status: Expired - Lifetime (US patent term expired)

DB cross-check: Against the DB entry "Nichia Corporation, Shuji Nakamura. 1993 realization, multiple patents," this yields two corrections, no match confirmation.

• DB correction 1 (inventors): DB "Shuji Nakamura solo" is incorrect → actually co-invented by Nakamura, Mukai, and Iwasa (three persons). Nakamura is widely recognized as the inventor of the patent's core (the proprietary two-flow MOCVD apparatus for p-type GaN crystal growth and the InGaN quantum well structure), but the patent's inventor field lists all three.
• DB correction 2 (Original Assignee): DB "Nichia Corporation" is incorrect → at filing, the company name was Nichia Chemical Industries Ltd (the 1956 founding name, used until the 2003 corporate name change). The Current Assignee is correctly Nichia Corporation.

Day 8–18 has accumulated 22 corrections and 12 match confirmations. The correction sequence resumes after the three consecutive matches at Day 17 ep65/66 / Day 18 ep67.

Claim 1 (verbatim from primary source)

Claim 1 retrieved verbatim from Google Patents:

A light-emitting gallium nitride-based compound semiconductor device having a double-heterostructure comprising: a light-emitting layer (active layer) having first and second major surfaces and formed of a low-resistivity In_x Ga_(1-x) N (0 less than x less than 1) compound semiconductor doped with an impurity; a first clad layer joined to the first major surface of the light-emitting layer and formed of an n-type gallium nitride-based compound semiconductor having a composition different from that of the compound semiconductor of the light-emitting layer; and a second clad layer joined to the second major surface of the light-emitting layer and formed of a low-resistivity, p-type gallium nitride-based compound semiconductor having a composition different from that of the compound semiconductor of the light-emitting layer.

Three points in Claim 1's core:

1. Realization of an In_x Ga_(1-x) N active layer in a single InGaN system: the composition x changes the emission wavelength, allowing continuous tuning from blue (x ≈ 0.1–0.2) to green (x ≈ 0.3–0.4). This enables visible-light coverage that GaN alone (UV) cannot.
2. Double-heterostructure with n-type GaN clad + p-type GaN clad: sandwiching the active layer with differently composed clads on both sides strengthens carrier confinement and improves quantum efficiency. Explicitly stating "low-resistivity p-type" in Claim 1 was groundbreaking at the time, since high resistivity in p-type GaN had been a long-standing wall for GaN-based blue LEDs.
3. Explicit composition difference in the three-layer structure (clad / active / clad): not a simple p-n junction, but a compositional separation between active and clad layers that secures design freedom.

Specification pitfall: this patent did not invent GaN crystal growth itself. The core technology of GaN crystal growth (high-quality single-crystal GaN using a low-temperature buffer layer) was published by Akasaki and Amano at Nagoya University in 1986 (Appl. Phys. Lett. 48:353), and p-type GaN crystal growth was achieved by Amano and Akasaki in 1989 by Mg-doping plus low-energy electron-beam irradiation (Jpn. J. Appl. Phys. 28:L2112) — separate-lineage inventions. Nakamura's contributions are (i) high-quality GaN mass production via the two-flow MOCVD apparatus, (ii) p-type GaN low-resistivity by thermal treatment (Mg doping + nitrogen-atmosphere annealing), and (iii) mass production of high-brightness blue LEDs via the InGaN double-heterostructure — the third item is what this patent's Claim 1 covers.

Two DB corrections in detail — Nichia Corporation vs Nichia Chemical Industries

Takashi Mukai and Naruhito Iwasa were Nichia Chemical Industries researchers alongside Nakamura, jointly working on InGaN crystal growth and p-type GaN doping technology. The patent name field has all three as co-inventors, but secondary industry sources and award reporting tend to bring only Nakamura's name to the front. This is similar to the "divergence between paper / award reporting and patent inventor names" we saw in Day 11 propranolol (James Black absent), Day 12 sildenafil, and Day 9 PCR (Mullis solo award vs six co-inventors), but with the reverse-direction divergence here: all three are on the patent, but only Nakamura is in the spotlight for the award.

The company name "Nichia Chemical Industries Ltd" was used for 47 years from the 1956 founding until the December 1, 2003 rename to Nichia Corporation. At the time of this patent filing (1993), the Chemical Industries name was naturally in use; the "Nichia Corporation" appearing as Current Assignee is automatically inherited after the renaming.

Nakamura's compensation lawsuit against Nichia — 2001–2005

Nakamura joined Nichia Chemical Industries in 1979, was responsible for blue-LED development, and achieved InGaN LED mass production in 1993. He moved to UC Santa Barbara as professor in 2000.

The Tokyo District Court's ¥20 billion ruling was at the time the largest in Japanese employee-invention compensation litigation, sending shockwaves through the industry. In response, many Japanese companies revised employee-invention regulations within 2004, and the Patent Act was amended in June 2004 (Article 35 changing "appropriate consideration" to "appropriate benefits," favoring in-company procedures). This patent US5578839A is central among the Nichia blue-LED patents that became the subject of the lawsuit, but the lawsuit itself dealt with Japanese patent numbers (e.g., JP H6-152023).

2014 Nobel Prize in Physics — separation in the inventor field

The 2014 Nobel Prize in Physics was awarded to Akasaki (Nagoya University), Amano (Nagoya University), and Nakamura (then UC Santa Barbara) "for the invention of efficient blue light-emitting diodes which has enabled bright and energy-saving white light sources."

However, the inventor field of this patent US5578839A does not include Akasaki or Amano. This is because:

• Akasaki and Amano belong to the Nagoya University / Toyoda Gosei lineage with separate patents: 1986 GaN single-crystal growth (low-temperature buffer layer), 1989 p-type GaN crystal growth (Mg doping + low-energy electron-beam irradiation), filed jointly with Toyoda Gosei in the late 1980s through the 1990s.
• Nakamura belongs to the Nichia Chemical Industries lineage with separate patents: 1991 two-flow MOCVD apparatus development, 1992 InGaN double-heterostructure (this patent), 1993 p-type GaN thermal-treatment low-resistivity, 1994 high-brightness blue-LED mass production.

The two lineages were first officially bundled as "joint contributions to the blue LED invention" at the time of the Nobel award; as patents, they remained separated by organization and lineage. The absence of Akasaki/Amano from this patent's inventor field reflects that they had parallel patents on the Toyoda Gosei / Nagoya University side. This resembles Day 11 ICI beta-blockers (James Black central in the literature but absent from the patent inventor field), but with the difference that the absent inventors hold parallel separate-lineage patents themselves.

Modern correspondence hypothesis (speculation)

Reading the grading: identical is one row (white-LED core structure inheritance). LED lighting / LCD backlights / Mini-LED TVs are descendants, but mass-production scale, implementation form, and peripheral materials (phosphors, encapsulation resin, packaging) have diverged significantly over 30 years.

Unconfirmed

• Full text of the specification (only the Google Patents Abstract and Claim 1 retrieved; figures, examples, data tables unread)
• Full text of the 1989 Amano/Akasaki p-type GaN crystal growth paper (Jpn. J. Appl. Phys. 28:L2112) (only title confirmed)
• Full text of Nakamura's 1991 two-flow MOCVD paper (Jpn. J. Appl. Phys. 30:L1705 etc.)
• Original judgment documents from the Nakamura vs Nichia lawsuit (Tokyo District Court 2001–2004 / Tokyo High Court 2005)
• 2014 Nobel Prize in Physics award rationale (Royal Swedish Academy of Sciences; only summary confirmed)
• Parallel Toyoda Gosei / Nagoya University–lineage patents (Akasaki / Amano patent number list — separate-episode candidate)
• Internal Nichia contribution-allocation documents for the three (Nakamura / Mukai / Iwasa)
• 2003 Nichia name-change (Chemical Industries → Corporation) securities filings
• GaN power semiconductor patents (Innoscience / Navitas / GaN Systems) and their relationship to this patent

Next actions

1. Treat Akasaki / Amano p-type GaN crystal-growth patents (Toyoda Gosei / Nagoya University lineage, ~1989 filings) as a separate-episode subject
2. Treat Nakamura's two-flow MOCVD apparatus patent (Nichia Chemical Industries, ~1991 filing) on the "apparatus invention" axis
3. Treat Japanese patents related to the Nakamura vs Nichia lawsuit (JP H6-152023 etc.) on the "employee-invention compensation" axis
4. Treat GaN power semiconductor patents (Navitas / GaN Systems / Innoscience) on the "material-system inheritance" axis
5. This memo, alongside Day 18's Note ep67 (silicon solar cell) and ep69 (OLED), forms the "absorbing light / generating light / generating light in arbitrary form" semiconductor-optics 3-piece set, taking the light-generation (inorganic LED) side

Reference links

• US Patent US5578839A (Google Patents): https://patents.google.com/patent/US5578839
• 2014 Nobel Prize in Physics official: https://www.nobelprize.org/prizes/physics/2014/summary/
• Nichia Corporation official LED archive: https://www.nichia.co.jp/en/about_nichia/history.html

Sister articles in the series

• Episode 61 (HW #1): 1948 Bell Labs Bardeen-Brattain point-contact transistor US2524035
• Episode 64 (HW #2): 1979 Goodenough Li-ion US4302518A
• Episode 67 (HW #3, same Day 18 as this article): 1954 Bell Labs silicon solar cell US2780765A
• Episode 69 (HW Memo #5, same Day 18 as this article): 1980 Kodak Tang OLED US4356429A

Day 18 forms the semiconductor-optics 3-piece set: "absorbing light (HW-006 silicon solar cell) / generating light (HW-005 InGaN blue LED, this article) / generating light in arbitrary form (HW-009 Kodak OLED)".