MOCVD에 의한 LED 반도체 에피택시 성장

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Electronics & Semiconductors Global Industrial Scale $25 billion

개요

Metal-organic chemical vapor deposition (MOCVD) grows the precisely layered III-V semiconductor crystals (GaN, InGaN, AlGaN) that form the active regions of LEDs and laser diodes. The process deposits crystalline thin films one atomic layer at a time from metal-organic precursors and hydride gases at 600-1,100 degrees C. The 2014 Nobel Prize in Physics was awarded for the development of blue GaN LEDs, which combined with phosphor conversion enabled white LED lighting that is revolutionizing the $100+ billion lighting industry.

화학 공정

Trimethylgallium (TMGa) and ammonia (NH₃) are delivered to a heated sapphire or silicon substrate in a high-purity reactor at 1,000-1,100 degrees C for GaN growth. Multiple layers of different compositions (AlGaN, InGaN quantum wells) are grown by switching precursors. The InGaN active layer composition determines the emission wavelength. The full LED epitaxial structure includes n-type, active (MQW), and p-type layers totaling 5-10 microns.

Ga(CH₃)₃ + NH₃ →[1,050 degrees C] GaN + 3CH₄ (GaN epitaxy)
In(CH₃)₃ + NH₃ →[750 degrees C] InN + 3CH₄ (InGaN quantum well growth, In content controls wavelength)

원자재

Trimethylgallium (Ga(CH₃)₃, TMGa) — Reaction of GaCl₃ with CH₃MgCl (Gallium source)
Trimethylindium (In(CH₃)₃, TMIn) — Organometallic synthesis (Indium source (for InGaN))
Ammonia (NH₃) — Haber-Bosch process (Nitrogen source)
Sapphire substrates (Al₂O₃) — Kyropoulos or HEM crystal growth (Epitaxial substrate)

최종 제품

LED epitaxial wafers (GaN/InGaN on sapphire) — White LEDs, display backlights, UV LEDs, laser diodes (2-6 inch wafer diameter, MQW structure)

Environmental Impact

MOCVD uses highly toxic and pyrophoric metal-organic precursors. Ammonia consumption is high (only ~10% utilization efficiency). Methane byproduct contributes to greenhouse gas emissions. Advanced exhaust treatment systems (thermal and plasma scrubbers) are required.

안전 고려사항

⚠ Trimethylgallium and trimethylindium are pyrophoric — ignite in air
⚠ Ammonia is toxic and corrosive
⚠ Hydrogen carrier gas is extremely flammable
⚠ Arsine (AsH₃) used for GaAs devices is one of the most toxic industrial gases

최근 혁신

Micro-LED displays using individually addressable GaN LEDs are the next-generation display technology.
UV-C LEDs for water purification are replacing mercury lamps.
GaN power electronics for EV chargers and data centers are a rapidly growing application beyond lighting.