Zinc selenide (ZnSe) is a direct-bandgap II-VI semiconductor with a bandgap of ~2.67 eV at room temperature, placing its primary emission in the blue-green visible range (~465 nm). It crystallises in the zinc-blende structure. Key parameters: refractive index ~2.4–2.67 across the visible and near-IR, transmission window 0.45–21.5 µm (one of the broadest of any II-VI compound), low absorption in the mid-IR, and moderate thermal conductivity (~18 W/m·K).
ZnSe’s dominant applications leverage its exceptional optical properties rather than its electrical ones. As an IR optical material, ZnSe CVD-grown polycrystalline windows and lenses are standard in CO₂ laser optics (10.6 µm) and thermal-imaging optics (3–5 µm and 8–12 µm), where its broad transmission, low scatter, and mechanical durability are unmatched among low-cost alternatives. In photonics, ZnSe is used as an anti-reflection coating layer and as the substrate for mid-IR non-linear crystals in optical parametric oscillators (OPO).
The semiconductor and optoelectronic application space is smaller. Blue-green ZnSe LEDs and laser diodes were heavily researched in the early 1990s before GaN rendered them largely obsolete for blue emitters. The active current interest is in ZnSe-based quantum dots as a cadmium-free replacement for CdSe QDs in display backlighting and bioimaging, exploiting the size-tunable emission across the visible without the RoHS toxicity burden of cadmium.
In the Compound Semiconductors and Wide-Bandgap Semiconductors landscape, ZnSe occupies a specialised optical-materials niche rather than a power or logic role. It is distinct from Zinc Oxide (piezo/TCO/UV focus) and from the III-V semiconductors that dominate RF and power switching.
Frontier
See frontmatter frontier: block.