Zinc Selenide (ZnSe) Wafers for Research & Production 

Zinc Selenide (ZnSe) Wafer Applications and Properties

Zinc Selenide (ZnSe) is a wide-bandgap II–VI semiconductor with exceptional transparency in the visible and infrared spectral regions. Its combination of optical clarity, mechanical strength, and chemical stability makes it one of the most widely used materials for infrared optics, laser systems, and semiconductor epitaxy. ZnSe can be fabricated as bulk substrates, thin films, or epitaxial layers depending on the device requirement.

Optical and Structural Characteristics

ZnSe is characterized by a direct bandgap of approximately 2.67 eV at 300 K and a refractive index ranging from 2.4 to 2.7 across the visible and IR spectrum. It maintains excellent transmission from 0.5 µm up to 15 µm, making it an ideal choice for CO₂ laser optics, IR windows, and waveguides. The cubic zincblende structure ensures isotropic optical behavior and compatibility with GaAs and Si for heteroepitaxy. Its high resistivity and low absorption enable usage in high-power optical paths without thermal distortion.

Crystal Growth and Film Deposition

High-purity ZnSe single crystals are typically grown by the chemical vapor transport (CVT) or Bridgman methods, using ultra-clean Zn and Se precursors. These crystals are then oriented and sliced into wafers with tight control of crystallographic orientation. For epitaxial or thin-film applications, ZnSe can be deposited using MBE, MOCVD, or sputtering techniques. Among these, MBE allows atomic-level control for creating ZnSe/ZnS, ZnSe/ZnTe, or ZnSe/CdSe heterostructures with tunable band alignment.

During growth, maintaining a slightly Se-rich environment minimizes Se vacancies, which otherwise act as donors and increase free-carrier absorption. Conversely, a Zn-rich regime promotes smoother surfaces but may induce stacking faults. Growth temperatures typically range from 250 °C to 400 °C, and post-deposition annealing under Se vapor can further enhance film stoichiometry and optical quality.

Defect Control and Doping

Unintended native defects such as V_Se and Zn_i can influence conductivity and photoluminescence. Controlled doping with elements like Cl (n-type) or N (p-type) is used to achieve desired electrical properties. Compensation between donor and acceptor levels must be precisely balanced to preserve optical transparency in the IR range. For photonic and electroluminescent devices, p-type ZnSe remains challenging, but progress has been achieved via nitrogen plasma sources and codoping strategies.

Infrared and Laser Applications

• CO₂ Laser Optics: ZnSe windows and focusing lenses are standard in high-power 10.6 µm laser systems due to minimal absorption and high thermal conductivity (~18 W/m·K).
• Optical Coatings: Multilayer ZnSe-based coatings (ZnSe/ZnS or ZnSe/Ge) provide tailored reflectivity for IR filters and dichroic mirrors.
• Waveguides & Photonics: ZnSe thin films can serve as the guiding layer in mid-IR integrated photonic circuits, supporting low-loss propagation up to 12 µm.
• Nonlinear Optics: ZnSe exhibits a significant nonlinear refractive index (n₂ ≈ 1.2 × 10⁻¹³ cm²/W), enabling frequency conversion and harmonic generation applications.

Thermal, Mechanical, and Environmental Behavior

ZnSe offers moderate hardness (Knoop ~120 kg/mm²) and a relatively low thermal expansion coefficient (~7.6 × 10⁻⁶ K⁻¹). It is chemically stable in dry environments but can degrade under prolonged exposure to moisture or strong acids. Protective anti-reflective (AR) coatings are recommended for humidity-prone or outdoor optical systems. Mechanical polishing and precision lapping techniques are used to achieve λ/10 surface flatness and sub-nanometer roughness for IR-grade components.

Emerging Research and Heterostructures

ZnSe remains central in the study of II–VI semiconductor heterostructures, particularly for quantum wells and blue-green LEDs. Heteroepitaxy of ZnSe on GaAs, Si, or GaP provides platforms for optoelectronic integration and bandgap engineering. Recent advances in ZnSe/SiC and ZnSe/Al₂O₃ templates have enabled improved lattice matching and reduced defect density for infrared photonics and laser gain media.

Purchasing & Customization

• Available in single- or double-side polished wafers, with thicknesses from 200 µm to 3 mm.
• Custom diameters from 1″ to 3″, with optical- or semiconductor-grade specifications.
• Options for undoped, Cl-doped, or N-doped material upon request.
• Custom optical flats, coatings, or patterned wafers available for R&D integration.