Photoluminescence of Rare-Earth Ions in the Nanocrystalline GaAs/SnO2 Heterostructure and the Photoinduced Electrical Properties Related to the Interface

Abstract

Deposition of an SnO 2 thin film was carried out by sol-gel-dip-coating and doped with Ce 3+ or Eu 3+ , and a GaAs layer was deposited by resistive evaporation or sputtering. This investigation combines the emission properties of these rare-earth ions with the unique transport properties generated by the heterostructure assembly. Illumination with light with energy above the GaAs bandgap and below the SnO 2 bandgap drastically increases the GaAs/SnO 2 heterostructure conductance, which becomes practically temperature-independent. This was associated with the presence of interface conduction, possibly a two-dimensional electron gas at the GaAs/SnO 2 interface. This feature takes place only for the sample where the GaAs bottom layer is deposited via sputtering. Irradiation with energies above the SnO 2 bandgap only excites the top oxide layer. The heterostructure assembly GaAs/SnO 2 :Eu leads to emission from Eu 3+ , unlike SnO 2 deposition directly on a glass substrate, where the Eu 3+ transitions are absent. Eu emission comes along a broad band, located at a higher energy compared to Eu 3+ transitions, which are blue-shifted as the thermal annealing temperature increases. Luminescence from Ce 3+ ions in the heterostructure can be detected, but the ions overlap with emission from the matrix, and a cleaning procedure helps to identify Ce 3+ transitions.

Room temperature ammonia gas sensor using Nd-doped SnO2 thin films and its characterization

“…The metal oxide semiconductors show high electrical conductance with high transparency in the visible region which have the applications in solar cell, light-emitting diodes, and other optoelectronic devices [4]. In the metal oxide group semiconductors, tin oxide is one of the notable semiconductors and has a wide band gap with high transparency in the visible region [5]. The research about tin oxide semiconductor is encouraged due to the potential applications such as gas sensors, lightemitting diodes, and solar cell windows [6][7][8][9].Recently, antimony, phosphorus, zinc, strontium, fluorine, nickel, and zirconium-doped SnO 2 thin films are prepared and they are characterized [10][11][12][13][14][15][16].…”