Semiconductors are materials whose conductivity can be tuned by doping, gating, thickness and defect engineering, and the current research literature is mostly about extending that control beyond silicon into monolayer dichalcogenides, organic crystals, quantum-dot solids and polar nitrides, where the physics is now well characterised at lab scale but manufacturing is not addressed at all.
Summary
A semiconductor is a solid with an energy gap between its filled valence states and empty conduction states. Everything useful follows from being able to move that gap around and to put controlled numbers of carriers into it: dope it, gate it, strain it, thin it, put it in a cavity. The engineering parameters that decide device behaviour are the size and directness of the band gap, the effective mass of electrons and holes (which sets mobility), the carrier density achievable by doping, the dielectric response, and how efficiently heat leaves the active region.
The sources collected here are almost entirely condensed-matter and optics papers from 2024 to 2026, and they map the frontier rather than the industry. A large fraction concerns two-dimensional transition metal dichalcogenides, where the gap depends on layer count: scanning tunnelling spectroscopy on MBE-grown MoS2 from one to five layers shows the gap falling sharply with thickness, to values below the bulk gap, with conduction-band pinning vanishing above four layers. Others deal with organic molecular semiconductors, where crystal packing rather than molecular design governs transport: a previously unrecognised and thermodynamically stable polymorph of the benchmark material DNTT was found coexisting in commercial powders, and it changes the dimensionality of charge transport. Colloidal quantum-dot films, increasingly used in place of bulk semiconductors, were measured at thermal conductivities as low as 0.55 W/m/K because heat moves poorly through close-packed dot solids.
Evidence base
Open questions
- Does the ~4 fJ, picosecond all-optical switching seen in a single MoSe2 photonic crystal nanocavity survive integration into a multi-element circuit, and at what insertion loss and repetition rate?
- Can the deterministic dopant segregation and 0.70% strain channels found in vanadium-doped WS2 be controlled to specification across a wafer, or does the kinetic mechanism only reproduce at small flake scale?
- How many other benchmark organic semiconductors have unrecognised stable polymorphs in commercial supply, and does polymorph control change reported mobility rankings?
- Is the 0.55 W/m/K thermal conductivity of close-packed quantum-dot films a hard ceiling set by the dot-solid geometry, or can ligand and matrix engineering raise it enough for continuous-wave operation?
Assessment drafted 2026-08-31 from up to 18 KB sources using the technology-scorecard framework; scores are a draft read pending review.