Optoelectronic performance of Si/ MgSe heterojunctions as a visible light communication component

Abstract

Herein magnesium selenide thin films coated onto glass and Si substrates are studied and characterized. The films, prepared by the thermal vacuum evaporation technique under a vacuum pressure of 10−5 mbar, are structurally, morphologically, compositionally, optically, and electrically investigated. While films grown onto glass substrates showed the existence of cubic phases of MgSe and MgSe2, films coated onto Si substrates contained SiSe2. Replacement of glass substrates by Si highly improved the crystallinity of the films. In addition, the optical analyses on the films grown onto Si substrates indicated the formation of Si/ MgSe heterojunctions with valence and conduction band offsets of 0.95 eV and 0.40 eV, respectively. MgSe films are coated onto Si substrates and contacted with Ag contacts performed as photosensors suitable for vehicle visible light communications. The asymmetry (rectification ratios), the current responsivity, the noise equivalent power factor, and the detectivity of the devices reached 517, 0.73 A/W, 5.93 W/Hz1/2 and 5.8 Jones, respectively, at 4.3 V.