Substrates for Epitaxial Deposition

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Epitaxial Wafers for Research

UniversityWafer supplies standard and custom epitaxial wafers for semiconductor research, device development, materials characterization, MEMS, photonics, power electronics, and university laboratories.

Available structures may include epitaxial silicon wafers, multilayer silicon structures, GaN on SiC, GaN on sapphire, and epi-ready substrates for MBE, MOCVD, and CVD growth.

Research Request: Two-Layer Silicon Epi Wafer

A teaching assistant at a public university requested a custom two-layer silicon structure for further device fabrication.

Requested specifications:

  • Wafer diameter: 100 mm
  • Structure: Two-layer silicon wafer
  • Bottom layer: 500 µm n+ silicon
  • Bottom-layer dopant: Phosphorus
  • Bottom-layer concentration: Approximately 1 × 1019 cm−3
  • Top layer: 10 µm p-type silicon
  • Top-layer dopant: Boron
  • Top-layer concentration: Approximately 7 × 1015 cm−3
  • Top surface: Polished for additional layer fabrication
  • Optional backside metal: Approximately 1.5 µm aluminum contact layer
  • Quantity: 1–25 wafers

The researcher also requested guidance on whether epitaxial growth, ion implantation, or a combination of processes would be most appropriate for producing the desired doping profile and layer structure.

Reference #210870 for specifications and pricing.

How to Specify an Epitaxial Wafer

To request an accurate quote, provide as many of the following details as possible:

  • Substrate material
  • Wafer diameter
  • Crystal orientation
  • Substrate conductivity type
  • Substrate resistivity or dopant concentration
  • Epitaxial material
  • Epi-layer thickness
  • Epi conductivity type
  • Epi resistivity or dopant concentration
  • Single-side or double-side polish
  • Additional oxide, nitride, buffer, or metal layers
  • Required quantity

Get Your Epitaxial Wafer Quote FAST! Complete the form below or Buy Online and start researching today.





Can Sapphire Wafers Be Used for Epitaxial Growth?

Yes. Sapphire wafers are widely used as substrates for epitaxial growth because they offer high-temperature stability, chemical resistance, electrical insulation, and compatibility with several compound-semiconductor materials.

Sapphire is commonly used for GaN, AlN, AlGaN, ZnO, and other optical or electronic materials grown by molecular beam epitaxy, MOCVD, pulsed laser deposition, and related thin-film processes.

Research Request: Epi-Ready A-Plane Sapphire

A university postdoctoral researcher requested cleanroom-packed, epi-ready sapphire substrates for MBE growth.

Requested specifications:

  • Material: A-plane sapphire
  • Orientation: (11-20)
  • Orientation tolerance: ±0.1°
  • Diameter: 1 inch
  • Thickness: Approximately 0.3–0.8 mm
  • Surface finish: One-side polished
  • Packaging: Epi-ready and cleanroom packed
  • Quantity: 10 wafers

The researcher also requested:

  • 20 × 20 mm A-plane sapphire pieces
  • Thickness between approximately 0.3 and 0.8 mm
  • One-side-polished surfaces
  • Quantity of 10 pieces

The main concern was whether the substrates could be loaded into the MBE system without additional chemical cleaning or surface treatment.

Reference #101799 for specifications and pricing.

What Is Epitaxial Growth?

Epitaxial growth is the deposition of a crystalline layer on a crystalline substrate so that the deposited material follows the crystallographic arrangement of the underlying wafer. The word epitaxy comes from Greek roots meaning “arranged upon.”

Unlike an amorphous or polycrystalline coating, an epitaxial layer has an ordered crystal structure. The relationship between the deposited layer and substrate allows engineers to create semiconductor materials with carefully controlled electrical, optical, and structural properties.

Epitaxy is used to fabricate semiconductor devices including transistors, integrated circuits, LEDs, laser diodes, photodetectors, solar cells, power devices, and quantum structures.

What Does Epitaxial Mean?

The term epitaxial describes a crystalline film whose orientation is influenced by the crystalline substrate beneath it. In many homoepitaxial structures, the deposited layer and substrate are made from the same material. For example, a silicon layer may be grown on a silicon wafer.

In heteroepitaxy, the deposited layer and substrate are different materials. Examples include GaN grown on sapphire, GaN grown on SiC, and compound-semiconductor layers deposited on silicon.

Homoepitaxy vs. Heteroepitaxy

  • Homoepitaxy: The epitaxial layer and substrate are the same material, such as silicon grown on silicon.
  • Heteroepitaxy: The epitaxial layer and substrate are different materials, such as GaN grown on sapphire or silicon carbide.

Common Epitaxial Growth Techniques

Why Epitaxial Layer Quality Matters

The performance of an epitaxial wafer depends on the quality and uniformity of the deposited layer. Important parameters include:

  • Layer thickness and thickness uniformity
  • Crystal orientation
  • Defect and dislocation density
  • Dopant concentration
  • Electrical resistivity
  • Composition and interface quality
  • Surface roughness
  • Wafer bow and stress

Precise control of these properties allows researchers and device manufacturers to tailor wafers for photonics, quantum devices, power electronics, MEMS, integrated circuits, and advanced sensor technologies.

What Is an Epitaxial Wafer?

An epitaxial wafer, often called an epi wafer, consists of a crystalline layer grown on a crystalline substrate. During epitaxial growth, the deposited layer follows the crystallographic structure and orientation of the underlying wafer.

Epitaxy allows engineers to control the layer thickness, composition, conductivity type, dopant concentration, resistivity, and interface quality. These properties make epitaxial wafers important for transistors, integrated circuits, LEDs, photodetectors, power devices, MEMS, radio-frequency electronics, and advanced semiconductor research.

UniversityWafer supplies epitaxial silicon wafers, GaN on SiC wafers, GaN on sapphire wafers, epi-ready substrates, and other custom semiconductor structures.

Epitaxial Growth Methods

The most suitable epitaxial deposition method depends on the substrate, deposited material, required layer quality, thickness, composition, and intended device.

  • Chemical Vapor Deposition (CVD): Uses gaseous precursors to deposit crystalline films and is widely used for silicon epitaxy.
  • Metal-Organic Chemical Vapor Deposition (MOCVD): Commonly used to grow GaN, AlGaN, InGaN, GaAs, and other compound-semiconductor layers.
  • Molecular Beam Epitaxy (MBE): Provides highly controlled growth under ultra-high-vacuum conditions and is frequently used for research-scale heterostructures and quantum materials.
  • Liquid Phase Epitaxy (LPE): Grows crystalline layers from a saturated liquid solution and may be used for selected compound-semiconductor structures.

GaN/AlN/SiC Epitaxial Wafers

GaN/AlN/SiC structures combine a gallium nitride device layer with an aluminum nitride buffer and a silicon carbide substrate. The AlN layer helps manage lattice and thermal mismatch, while SiC offers high thermal conductivity and mechanical stability.

These epitaxial structures are used in applications such as:

  • High-electron-mobility transistors
  • RF and microwave electronics
  • High-power semiconductor devices
  • Ultraviolet and visible optoelectronics
  • Synchrotron and surface-science research
  • Advanced GaN material characterization

Research Request: GaN/AlN/SiC and GaN/AlN/Sapphire

A chemical physics professor requested pricing for 50 mm, on-axis, n-type GaN/AlN structures for synchrotron radiation research.

Requested specifications:

  • Structure: GaN/AlN/SiC or GaN/AlN/Al2O3
  • Diameter: 50 mm
  • Orientation: On-axis
  • Conductivity: N-type
  • GaN thickness: Approximately 0.5–0.8 µm
  • AlN thickness: Approximately 0.1 µm
  • Quantity: 1 or 5 wafers

Reference #91327 for specifications and pricing.

Gallium Nitride Epitaxial Wafers

GaN on SiC is commonly selected for high-power and high-frequency devices because silicon carbide conducts heat efficiently and can support high-quality GaN layers.

GaN on sapphire is widely used for LEDs, photodetectors, optical devices, and GaN process development. Sapphire provides good optical transparency and is available in several standard wafer diameters and orientations.

Research Request: GaN on SiC and Sapphire

A semiconductor company requested availability and pricing for:

  1. GaN on 6H-SiC, 50 mm diameter, on-axis, n-type, with an approximately 0.5 µm GaN layer.
  2. GaN on sapphire, 50 mm diameter, on-axis, n-type, with a GaN thickness between approximately 0.5 and 10 µm.
  3. Two-inch 6H-SiC substrates with single-side or double-side polish.
  4. Two-inch p-type silicon substrates with double-side polish.

Reference #90172 for specifications and pricing.

Epitaxial Silicon Wafers

Epitaxial silicon wafers contain a controlled single-crystal silicon layer deposited on a silicon substrate. The epitaxial layer and handle wafer may have different dopants, resistivities, and conductivity types.

Common silicon epi configurations include:

  • N-type epi on an n+ substrate
  • P-type epi on a p+ substrate
  • P-type epi on an n-type substrate
  • N-type epi on a p-type substrate
  • Intrinsic or lightly doped epi layers
  • Single-layer and multilayer epitaxial structures

Researchers may specify the wafer diameter, substrate orientation, epi-layer thickness, substrate resistivity, epi resistivity, dopant species, polish, oxygen concentration, and allowable defect density.

Research Request: Thin N/N+ Silicon Epi Wafers

A nanomaterials researcher requested:

  • Crystal orientation: <111>
  • Structure: N-type epi on an n+ substrate
  • Epi-layer thickness: 500 nm to 1 µm
  • Preferred epi resistivity: Approximately 0.1 ohm-cm
  • Preferred substrate resistivity: Less than 0.01 ohm-cm
  • Priority: In-stock material and short delivery time

Reference #103430 for specifications and pricing.

Epitaxial Layers on SOI Wafers

An epitaxial silicon layer may be grown on the crystalline device layer of a silicon-on-insulator wafer when the surface condition, orientation, thermal budget, and process requirements are compatible with epitaxial deposition.

Epitaxial growth can increase the device-layer thickness or create a controlled doping profile while preserving the electrical isolation provided by the buried oxide. This approach may be useful for MEMS, sensors, photonics, power devices, and specialized transistor structures.

A semiconductor researcher requested:

  • A 2–4 µm crystalline silicon layer
  • P-type or n-type conductivity
  • An insulating substrate or oxidized silicon structure
  • Small research quantities of approximately two or three wafers
  • Possible epitaxial growth on 50 × 50 mm silicon-on-glass samples

Reference #94309 for specifications and pricing.

PN Junctions at the Wafer/Epi Interface

A PN junction can be formed at the interface between an epitaxial layer and its substrate by selecting opposite conductivity types. For example, a p-type epi layer may be grown on an n-type substrate, or an n-type epi layer may be grown on a p-type substrate.

This configuration allows engineers to control the junction depth, doping transition, depletion region, breakdown voltage, and electrical behavior of the resulting device.

A microstructure physics researcher requested four-inch silicon wafers with either a p-type or n-type substrate and an oppositely doped epitaxial layer so that a PN junction would form at the substrate/epi interface.

Reference #106430 for specifications and pricing.

Epitaxial Transistors

An epitaxial transistor uses one or more epitaxially grown semiconductor layers to form or support the active device regions. In a bipolar junction transistor, the epitaxial layer may be engineered as part of the collector region. Epitaxy is also used in MOSFETs, high-electron-mobility transistors, and RF devices.

Cross-sectional diagram of an epitaxial transistor showing the emitter, base, collector, and epitaxial layers Epitaxial layers provide several device-design advantages:

  • Controlled doping profiles: Layer conductivity and dopant concentration can be tailored for the required device behavior.
  • Lower defect density: High-quality growth can provide a controlled active layer with fewer electrically significant defects.
  • Improved breakdown performance: A lightly doped epi layer on a heavily doped substrate can support higher voltage while maintaining a low-resistance electrical contact.
  • Reduced parasitic effects: Properly engineered epitaxial layers can reduce unwanted resistance and capacitance.
  • Device isolation: Epitaxial structures may support junction isolation or other electrical isolation techniques.

Materials Used for Epitaxial Transistors

  • Silicon: Used for conventional bipolar transistors, CMOS devices, power devices, and integrated circuits.
  • Silicon-Germanium: SiGe epitaxy is used in high-speed bipolar and RF devices because germanium can improve carrier transport when incorporated into silicon structures.
  • Gallium Arsenide: Used in high-frequency electronics, optoelectronics, lasers, and specialized RF devices.
  • Gallium Nitride: Used for high-power, high-frequency, and high-temperature semiconductor applications.

Epitaxial Graphene Research

Epitaxial graphene may be studied on silicon carbide or transferred to silicon-based substrates for optical, electrical, and spectroscopic measurements.

A physics professor requested double-side-polished Si/SiO2 substrates for infrared spectroscopy and back-gated graphene measurements.

The project required a compromise between optical transmission and electrical conductivity, along with a surface suitable for large-area graphene deposition.

Reference #143652 for specifications and pricing.

Multilayer Epitaxial Silicon Wafers

Multilayer epi wafers combine a silicon substrate with one or more epitaxial, dielectric, or conductive layers. These structures may be designed to provide different electrical properties at specific depths within the wafer.

A researcher requested the following three-layer structure:

  1. Bulk p-type silicon substrate, approximately 0.5 mm thick
  2. Thin, higher-conductivity p-type epitaxial silicon layer, approximately 2 µm thick
  3. Silicon dioxide layer, approximately 3.6 µm thick

Reference #103963 for specifications and pricing.

LED Epitaxial Wafers

An LED epitaxial wafer contains a sequence of crystalline semiconductor layers engineered to generate light when electrons and holes recombine in the active region.

Blue and green LEDs commonly use GaN and InGaN layers grown on sapphire or silicon carbide. Other LED wavelengths may use gallium arsenide and related III-V semiconductor materials.

Typical LED Epitaxial Structure

  1. Substrate: Provides the mechanical foundation for epitaxial growth.
  2. Buffer or nucleation layer: Helps accommodate lattice mismatch between the substrate and the device layers.
  3. N-type layer: Supplies electrons to the active device structure.
  4. Multiple quantum well active region: Generates light through electron-hole recombination.
  5. P-type layer: Supplies holes and completes the diode structure.

A postdoctoral researcher requested small quantities of blue or green LED wafers with a p-GaN/MQW/n-GaN/u-GaN/sapphire structure, as well as undoped and n-type GaN-on-sapphire options.

Layer structure of blue and green GaN LED epitaxial wafers

How to Specify an Epitaxial Wafer

Providing complete specifications helps identify an available wafer or determine whether a custom epitaxial structure is required.

  • Substrate material and diameter
  • Crystal orientation and offcut
  • Substrate conductivity type and resistivity
  • Epitaxial material and layer sequence
  • Epi-layer thickness
  • Dopant species and concentration
  • Target epi-layer resistivity
  • Single-side or double-side polish
  • Additional oxide, nitride, metal, or buffer layers
  • Required quantity and delivery schedule

UniversityWafer supplies standard and custom epitaxial substrates for university research, process development, prototype fabrication, and semiconductor production.

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