UniversityWafer supplies undoped silicon wafers and high-resistivity silicon substrates for semiconductor research, spectroscopy, photonics, MEMS, sensors, and device fabrication. Choose from multiple wafer diameters, crystal orientations, thicknesses, and SSP or DSP surface finishes. High-resistivity Float Zone (FZ) silicon is available for applications requiring low oxygen concentration and reduced free-carrier effects. Order small quantities for research or request custom silicon wafer specifications.
UniversityWafer supplies undoped silicon wafers and high-resistivity silicon wafers for research, spectroscopy, photonics, MEMS, sensors, thin-film deposition, and semiconductor device development. Researchers can order small quantities for prototyping or request custom specifications for more specialized experiments.
Available specifications may include different wafer diameters, thicknesses, crystal orientations, resistivity ranges, and single-side polished (SSP) or double-side polished (DSP) surfaces. High-resistivity Float Zone (FZ) silicon is particularly useful when low oxygen concentration and reduced free-carrier effects are important.
A Graduate Research Assistant requested the following:
We need 4-inch undoped silicon wafers with oxide thicknesses of 20 nm, 50 nm, 100 nm, 150 nm, 200 nm, and 250 nm.
Can all of the wafers be produced from the same silicon boule ?
Could you also specify the price for 4-inch undoped Si wafers from the same boule with <100> orientation, including wafers without the oxide layer?
Reference #210773 for specifications and pricing.
Silicon described commercially as undoped generally means that no dopant has been intentionally introduced to establish a specified p-type or n-type conductivity. Real silicon crystals can still contain residual electrically active impurities and defects, so an undoped wafer should not automatically be assumed to behave as perfectly intrinsic silicon.
For many research applications, the more useful specification is therefore silicon resistivity. UniversityWafer inventory includes high-resistivity material, with selected wafers available at resistivities up to and above 20,000 Ω·cm.
High-resistivity silicon has a lower concentration of electrically active free carriers than heavily doped silicon. This can reduce free-carrier absorption and electrical losses in applications where substrate conductivity would otherwise interfere with a measurement or device.
These properties make high-resistivity silicon useful for selected spectroscopy, RF and microwave research, photonics, detector development, MEMS, and materials characterization applications. The appropriate resistivity, thickness, orientation, and growth method should always be selected for the specific experiment.
Need a specific wafer? Get your undoped silicon wafer quote FAST! Or buy undoped silicon wafers online and start researching today.
Researcher Question:
We are working on a Senior Design Project to create a biobattery. We need a substrate that can be patterned using photolithography and subsequently coated with metal films that will serve as catalytic and electrically conductive structures. What type of silicon wafer should we consider?
UniversityWafer Response:
Silicon is a widely used substrate for this type of research because it is compatible with established microfabrication processes including photolithography, thin-film deposition, etching, and surface modification. However, the best wafer specification depends on how the substrate will function in the device.
If the silicon is intended primarily as a mechanically stable substrate for patterned metal films, an undoped or high-resistivity wafer may help reduce unwanted electrical conduction through the substrate. If the silicon itself must act as an electrode or electrically active device region, a controlled p-type or n-type silicon wafer with a specified resistivity may instead be required.
Surface condition is also important. A polished silicon surface is generally preferred for photolithography and thin-film processing because surface roughness and defects can affect resist coating, pattern transfer, and film uniformity.
For budget-sensitive proof-of-concept work, researchers can also review the current undoped silicon wafer inventory and select an available specification appropriate for the experiment.
Silicon wafers are also used as starting materials or experimental substrates in materials-science research. One example is electrical explosion of wires (EEW), a pulsed-energy technique in which a high current rapidly heats and vaporizes a conductive wire or filament. The resulting vapor can cool and condense into nanoscale particles under suitable experimental conditions.
Researchers investigating other semiconductor materials may also consider germanium wafers. Material selection for these experiments depends strongly on the electrical, thermal, mechanical, and dimensional requirements of the experimental setup.
UniversityWafer can supply silicon substrates with different thicknesses and can provide wafer processing services for specialized research requirements. See our silicon wafer resources for additional substrate options.
UniversityWafer maintains an inventory of undoped and high-resistivity silicon wafers for research and device development. Available specifications vary by diameter, crystal orientation, resistivity, thickness, and surface finish.
The examples below include wafers with resistivities from approximately 1,000 Ω·cm to greater than 20,000 Ω·cm. Inventory changes frequently, so check the online store for current specifications and availability.
Buy as few as one undoped silicon wafer online.
| ID | Diameter | Dopant | Orientation | Resistivity (Ω·cm) | Thickness (µm) | Polish |
|---|---|---|---|---|---|---|
| 2313 | 25.4 mm | Undoped | <111> | >2,000 | 280 µm | SSP |
| 2483 | 25.4 mm | Undoped | <100> | >5,000 | 73.5 µm | DSP |
| 2018 | 50.8 mm | Undoped | <100> | >10,000 | 280 µm | DSP |
| 3032 | 100 mm | Undoped | <100> | 1,000–3,000 | 500 µm | SSP |
| 3193 | 100 mm | Undoped | <100> | >10,000 | 525 µm | DSP |
| 3328 | 100 mm | Undoped | <100> | >20,000 | 525 µm | SSP |
| 3225 | 150 mm | Undoped | <100> | >10,000 | 675 µm | DSP |
An undoped silicon wafer is a crystalline silicon substrate manufactured without intentionally adding a dopant to establish a specified p-type or n-type conductivity. The term is commonly used commercially for high-purity or high-resistivity silicon intended for applications where controlled low carrier concentration is desirable.
It is important to distinguish undoped silicon from an ideal intrinsic semiconductor. Intrinsic silicon is a theoretical or highly purified material in which electron and hole concentrations are determined primarily by thermal generation rather than intentional dopants. A real commercially produced undoped wafer can contain trace impurities, native defects, and residual electrically active species. As a result, it may exhibit weak n-type or p-type conductivity even though no intentional dopant was specified.
For this reason, researchers should consider the measured silicon resistivity and other material specifications rather than assuming that every wafer labeled "undoped" has identical electrical properties.
Intentional doping changes the carrier concentration and electrical properties of crystalline silicon. Common acceptor dopants such as boron produce p-type silicon, in which holes are the majority carriers.
Common donor dopants such as phosphorus, arsenic, and antimony can produce n-type silicon, in which electrons are the majority carriers.
Increasing the electrically active dopant concentration generally increases the majority-carrier concentration and decreases the material's resistivity, although the exact relationship also depends on carrier mobility, temperature, dopant activation, and material quality.
Neither doped nor undoped silicon is universally "better." The appropriate material depends on the application. Controlled doping is essential for semiconductor devices such as diodes, transistors, solar cells, and integrated circuits, while high-resistivity silicon is advantageous when electrical isolation or reduced free-carrier effects are required.
"Undoped" means that a conductivity-controlling dopant was not intentionally introduced. It does not necessarily mean that the finished crystal contains absolutely no electrically active impurities.
Trace impurities and crystal defects introduced during silicon growth and processing can create a small imbalance between donor-like and acceptor-like states. Consequently, nominally undoped silicon can exhibit weak n-type or p-type behavior while still maintaining very high resistivity.
This is different from a deliberately doped wafer, where elements such as boron, phosphorus, arsenic, or antimony are intentionally incorporated to obtain a targeted conductivity type and resistivity.
It is also different from degenerate silicon. Degenerate silicon is intentionally doped to such a high carrier concentration that conventional nondegenerate semiconductor approximations no longer adequately describe its electronic behavior. It should not be confused with intrinsic or nominally undoped silicon.
High-resistivity silicon is useful when electrical conduction through the substrate could interfere with a device or measurement. Depending on the wavelength and experimental configuration, reducing the free-carrier concentration can also reduce free-carrier absorption and associated electromagnetic losses.
Applications can include selected forms of:
Float Zone (FZ) silicon is frequently selected for high-resistivity applications because the crucible-free Float Zone growth process generally produces much lower oxygen concentrations than conventional Czochralski-grown silicon.
A university laboratory manager requested a wafer for the following experiment:
I need a silicon wafer for spectroscopic measurements inside a cryostat, so the substrate should be relatively thin.
I would also like to minimize unwanted optical or electronic background from the substrate. What undoped silicon wafer specifications should I consider?
Reference #251682 for specifications and pricing.
There is no single silicon wafer specification that is optimal for every spectroscopic measurement. Silicon has strongly wavelength-dependent optical properties, and substrate selection should be based on the spectral range, temperature, optical geometry, and signal being measured.
Important specifications can include:
Resistivity: High-resistivity silicon has a lower free-carrier concentration than heavily doped silicon and can therefore reduce free-carrier-related optical and electrical losses in appropriate spectral ranges.
Growth Method: High-resistivity FZ silicon is often useful for optical, microwave, and detector research because of its low oxygen concentration and high achievable resistivity.
Thickness: Wafer thickness affects optical path length, absorption, interference behavior, mechanical rigidity, and compatibility with cryogenic sample holders.
Surface Finish: A polished silicon surface minimizes scattering associated with surface roughness. DSP wafers may be preferable for transmission measurements where light passes through both wafer surfaces.
Crystal Orientation: Common silicon orientations include <100>, <110>, and <111>. Orientation can be important when the experiment involves anisotropic etching, surface chemistry, crystallographic characterization, or orientation-dependent device processing.
Oxygen and Impurity Concentration: Oxygen, carbon, metallic impurities, and electrically active defects can influence electrical and optical measurements. The acceptable impurity level therefore depends on the sensitivity and spectral range of the experiment.
Surface Oxide: Silicon exposed to air naturally develops a thin native oxide. This surface layer can influence surface-sensitive optical measurements and should be considered when the experiment depends strongly on the silicon/ambient interface.
Temperature: Carrier concentration, carrier mobility, absorption, and other material properties change with temperature. Cryogenic spectroscopy therefore requires consideration of silicon properties at the actual measurement temperature rather than relying only on room-temperature specifications.
When requesting an undoped or high-resistivity silicon substrate, specify as many experimental requirements as possible, including:
Providing these specifications makes it easier to select a silicon substrate whose electrical, optical, mechanical, and crystallographic properties are appropriate for the intended experiment.
Need help selecting a substrate? UniversityWafer can provide standard inventory as well as custom silicon wafer specifications for research and development.