The key figures of merit are the specific detectivity D*, cutoff wavelength λ_c (determined by composition), and operating temperature. MWIR HgCdTe can achieve background-limited performance (BLIP) at 77–200 K; LWIR arrays typically require 77 K cryocooling. High electron mobility (~10⁵ cm²/V·s at 77 K) and low effective mass also support electron-APD (eAPD) operation: in a thin multiplication region, the electron impact-ionisation coefficient dominates strongly over the hole coefficient, giving near-noiseless single-photon gain — an advantage InGaAs cannot match.
Substrate choices (CdZnTe bulk, CdTe/Si) and MOVPE vs LPE growth govern uniformity and scalability. Moon Photonics builds mid-wave HgCdTe detector arrays sitting within this material class. HgCdTe eAPDs increasingly compete with SPAD arrays for lidar and FLIM applications in the 1–5 µm band.
Frontier
- Can MOVPE-grown HgCdTe on silicon substrates reach military-grade uniformity at commercial cost, or does lattice mismatch remain a disqualifier?
- Will avalanche-mode HgCdTe (eAPD) displace InGaAs APDs for 1–5 µm single-photon sensing, given HgCdTe’s near-unity impact-ionisation ratio?
- At what CdTe composition does the Type-III (semimetal) crossover set a practical bandgap floor for room-temperature MWIR operation?