Optical and Photosensitive Properties of Flexible n ( p )-InSe/In 2 O 3 Heterojunctions.

In this work, optical, including photoluminescence and photosensitivity, characteristics of micrometer-sized flexible n ( p )-InSe/In 2 O 3 heterojunctions, obtained by heat treatment of single-crystalline InSe plates doped with (0.5 at.%) Cd (Sn), in a water-vapor- and oxygen-enriched atmosphere, are investigated. The Raman spectrum of In 2 O 3 layers on an InSe:Sn substrate, in the wavelength range of 105-700 cm -1 , contains the vibration band characteristic of the cubic (bcc-In 2 O 3 ) phase. As revealed by EDX spectra, the In 2 O 3 layer, ~2 μm thick, formed on InSe:Cd contains an ~18% excess of atomic oxygen. The absorption edge of InSe:Sn (Cd)/In 2 O 3 structures was studied by ultraviolet reflectance spectroscopy and found to be 3.57 eV and ~3.67 eV for InSe:Cd and InSe:Sn substrates, respectively. By photoluminescence analysis, the influence of doping impurities on the emission bands of In 2 O 3 :Sn (Cd) was revealed and the energies of dopant-induced and oxygen-induced levels created by diffusion into the InSe layer from the InSe/In 2 O 3 interface were determined. The n ( p )-InSe/In 2 O 3 structures display a significantly wide spectral range of photosensitivity (1.2-4.0 eV), from ultraviolet to near infrared. The influence of Cd and Sn concentrations on the photosensitivity and recombination of nonequilibrium charge carriers in n ( p )-InSe layers from the heterojunction interface was also studied. The as-obtained nanosized InSe/In 2 O 3 structures are suitable for optoelectronic applications.