Metal-Organic Chemical Vapor Deposition (MOCVD) is a critical technique for growing high-quality InP (Indium Phosphide) epitaxial wafers, which are essential for optoelectronic devices (lasers, photodetectors) and high-frequency electronics. Several key MOCVD reactor models are widely used in the industry and research for InP growth. Here are the most prominent ones:
1. AIXTRON (Now part of ASM International)
- AIX 2800G4 & G5
- Popular for III-V semiconductor growth, including InP.
- Features a Planetary Reactor® design for uniform deposition.
- Used for high-volume production of InP-based devices.
- AIX 300/4 & AIX 200/4
- Suitable for R&D and small-scale production.
- Precise control over gas flows and temperature for InP and related alloys (InGaAs, InAlAs).
2. Veeco (Now part of Riber)
- Veeco Propel™ GaN & Compound Semiconductor MOCVD
- Originally designed for GaN but adapted for InP growth.
- High uniformity and low defect density.
- Veeco TurboDisc® K465i
- Used for both GaAs and InP-based materials.
- Good for high-throughput production.
3. Nippon Sanso (Now part of Taiyo Nippon Sanso)
- SR-4000 & SR-6000 Series
- Widely used in Japan and Asia for InP epitaxy.
- High-precision gas control for InP, InGaAsP, and related materials.
4. Thomas Swan (Now part of AIXTRON)
- Close Coupled Showerhead (CCS) Reactors
- Known for excellent uniformity and low defect growth.
- Used for both research and production-scale InP epitaxy.
5. Riber
- Riber Epineat & Riber Compact
- French-made systems used in research labs for InP and related III-V materials.
- Good for low-volume, high-precision epitaxy.
Key Considerations for InP MOCVD Growth
- Precursor Gases: Trimethylindium (TMIn) and phosphine (PH₃) are commonly used.
- Substrate Temperature: Typically 550–650°C for InP growth.
- Uniformity & Defect Control: Critical for optoelectronic applications.
- Doping Control: Precise n-type (Si, Te) and p-type (Zn, Mg) doping is essential.
Conclusion
The AIXTRON G4/G5 and Veeco Propel/K465i are among the most widely used MOCVD systems for InP epitaxy, especially in commercial production. For research labs, Thomas Swan CCS and Riber systems are also popular. The choice depends on throughput, uniformity requirements, and budget.
Would you like recommendations for specific applications (e.g., lasers, photodiodes, or HEMTs)?
To accurately measure optical and electrical performance—specifically **$L\text{-}I\text{-}V$ curves, optical spectra, near-field patterns (NFP), and far-field patterns (FFP)**—raw semiconductor laser dies cannot be tested as standalone chips because of thermal self-heating and current injection limitations.
The standard industry approach for chip-level characterization uses a **Chip-on-Submount (COS)** package or a **C-Mount / CS-Mount carrier**.
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## 1. The Primary Carrier Format: Chip-on-Submount (COS)
For characterization, the laser die is die-attached onto an intermediate high-thermal-conductivity submount.
### Standard COS Assembly Steps:
1. **Submount Material Selection:**
* **Aluminum Nitride ($\text{AlN}$):** Thermal conductivity $\approx 170\text{–}200\text{ W/m}\cdot\text{K}$. Its Coefficient of Thermal Expansion ($\text{CTE} \approx 4.5 \times 10^{-6}/\text{K}$) matches InP ($\approx 4.6 \times 10^{-6}/\text{K}$), preventing thermal stress and mechanical cracking during soldering and operation.
* **Diamond Submounts:** Used for extreme high-power testing ($\sim 2000\text{ W/m}\cdot\text{K}$).
2. **Die Attachment (Junction-Down vs. Junction-Up):**
* **Junction-Down (P-side down):** Essential for continuous-wave (CW) power testing. Placing the active layer directly against the submount provides the shortest thermal path to the heatsink.
* **Solder:** Gold-Tin ($\text{Au}_{80}\text{Sn}_{20}$) eutectics pre-deposited on the submount ($\text{melting temp} \approx 280^\circ\text{C}$) are standard for void-free thermal contact.
3. **Electrical Contacts:**
* **Wire Bonding:** Gold wires ($25\ \mu\text{m}$ diameter) or ribbon bonds connect top contact pads to traces on the ceramic submount.
* **Facet Overhang:** The laser emitting facet must overhang the submount edge slightly ($5\text{–}10\ \mu\text{m}$) to prevent solder wicking onto the facet coating and to avoid obscuring the large-angle far-field emission.
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## 2. Mounting onto a Test Fixture / C-Mount
Once assembled onto the submount, the COS is mounted onto a mechanical testing block:
* **C-Mount or CS-Mount:** A copper block (nickel/gold-plated) that provides thermal mass and a mechanical interface for clamping onto a thermoelectric cooler (TEC) fixture.
* **Open-Facet Access:** The front facet remains completely unobstructed, allowing direct optical collection via integrating spheres, lensed fibers, or beam profiling cameras.
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## 3. How Specific Measurements Are Conducted
1. **L-I-V Curves (Light-Current-Voltage):** Power and diode threshold characterization.
* Mount the C-Mount/COS onto a temperature-controlled cold plate (stabilized via TEC at $25^\circ\text{C}$).
* Place an **Integrating Sphere** or large-area Photodiode (InGaAs) directly in front of the emitting facet to capture total optical power without spatial clipping.
* Sweep injection current (pulsed or continuous-wave) and record optical output power and forward voltage.
2. **Optical Spectrum Analysis (OSA):** Wavelength, SMSR, and linewidth measurement.
* Position a polarization-maintaining (PM) lensed fiber or an objective lens in front of the laser facet.
* Couple the output light into an Optical Spectrum Analyzer (OSA) to verify peak wavelength, **Side-Mode Suppression Ratio (SMSR)**, and temperature tuning coefficients ($\text{d}\lambda/\text{d}T$).
3. **Far-Field Pattern (FFP):** Beam divergence angle measurement.
* Leave the facet unobstructed in free space.
* Use a goniometric radiometer or a rotating photodetector array swept on a spherical arc around the facet.
* Measure output intensity as a function of horizontal ($\theta_\Vert{}$) and vertical ($\theta_\perp$) angles to extract full-width at half-maximum (FWHM) divergence angles.
4. **Near-Field Pattern (NFP):** Facet spot profile and mode quality.
* Position a high-numerical-aperture ($\text{NA} > 0.5$) microscope objective close to the output facet.
* Project the magnified mode image onto an InGaAs beam profiling camera to measure spot size ($w_x, w_y$), verify single-transverse-mode profile, and inspect for facet defects.
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## Key Considerations During Packaging
* **Facet Cleanness:** Avoid epoxy degassing or organic contamination near the laser facet during assembly; unpassivated facets are prone to Catastrophic Optical Mirror Damage (COMD) under high power.
* **Avoid Wire Bond Parasitics:** Keep wire bonds as short as possible to prevent inductive ringing if testing high-speed dynamic response alongside DC parameters.
* **Facet Protection:** Ensure mechanical handling tools do not touch the front/rear anti-reflective (AR) or high-reflective (HR) coatings.
Buying custom metallized **AlN ceramic submounts** and **C-Mount test fixtures** requires sourcing from specialized semiconductor packaging suppliers and optoelectronic lab equipment vendors.
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## 1. Where to Buy Metallized Ceramic Submounts (COS Carriers)
Laser diode submounts are rarely off-the-shelf items because the **patterning, AuSn solder thickness, pad dimensions, and edge gap geometries** must match your specific die layout.
### Custom Thin-Film & Submount Fabricators
* **Remtec, Inc.:** Specializes in AlN and BeO ceramic submounts with pre-deposited $\text{AuSn}$ (80/20) eutectic solder pads and zero-pullback edge metallization designed for edge-emitting DFB lasers.
* **SemiGen:** Offers thin-film patterned AlN submounts with $\text{Ti/Pt/Au}$ and deposited $\text{Au/Sn}$ pads suited for InP laser die attachment.
* **TECNISCO:** Manufactures high-thermal-conductivity AlN and $\text{Cu-AlN-Cu}$ composite heat spreaders with micro-machined edge gap geometry.
* **Cutting Edge Optronics (Northrop Grumman):** Supplies custom ceramic and metallic submounts tailored for high-power semiconductor lasers.
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## 2. Where to Buy C-Mount Test Fixtures & TEC Mounts
For testing mounted dies or C-mount devices, off-the-shelf TEC-cooled laboratory fixtures are readily available.
### Commercial Test Fixture Suppliers
An active TEC-cooled mounting fixture designed specifically for characterization and thermal management of C-mount laser diodes.
Handles high thermal loads with active TEC cooling and a cold plate interface for $L\text{-}I\text{-}V$ testing.
* **Thorlabs:** Offers active TEC-cooled C-mount fixtures (such as the `LDMC20` series) featuring integrated cooling fans, DB9 connectors for TEC controllers, and open-facet access for optical collection.
* **Arroyo Instruments:** Provides C-mount and custom die submount fixtures (e.g., `242 TEC LaserMount`) with high thermal dissipation capacities.
* **Newport / MKS Instruments:** Supplies temperature-controlled laser mounts and fixture adapters compatible with industry-standard current and TEC controllers.
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