High-efficiency p–i–n detectors for the visible spectral range based on ZnSTe–ZnTe superlattices

We demonstrate that ZnSTe–ZnTe superlattices, which are grown lattice matched on GaAs substrates by molecular-beam epitaxy, are well suited as a material for light detection in the visible spectral range. Due to their type-II band alignment, these superlattices have a small band gap compared to ZnSe and allow light detection for photon energies between 2.1 and 3.2 eV. In combination with ZnMgSSe, the response curve of the diodes shows a strong dependence on the applied reverse bias, so that they can be used as two-color devices. The obtained external quantum efficiencies are as high as 70%, and dark currents as low as 10−12 A/mm2 were obtained.