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 match ed on GaAs substrates by molecular-beam epitaxy, are well suited as a mater ial 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 c ombination with ZnMgSSe, the response curve of the diodes shows a strong de pendence 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%, an d dark currents as low as 10(-12) A/mm(2) were obtained. (C) 1999 American Institute of Physics. [S0003-6951(99)05322-X].