The Poole-Frenkel conduction mechanismin Mo-Cu₂O-Au thin film structures

Abstract

Thin films of cuprous oxide (4.6 μm) were electrodeposited on molybdenum. Gold contacts were vacuum evaporated on the films to form devices. These films showed relatively low electrical resistivities at around 10⁶ Ω cm and a charge transport mechanism which is different from the space charge limited current conduction previously reported for the 10¹¹ Ω cm films. The charge transport mechanism in these films was determined by isothermal measurements of the devices current-voltage (I–V) characteristics at some selected temperatures in the range of 78–321 K. In this temperature range the dominant transport mechanism can be explained by the Poole-Frenkel effect through the relation I = VG₀exp(−φ_0L/kT)exp(B_LV^1/2)+I₀exp(−φ_0H/kT)exp(B_HV^1/2) where the numerical values of the parameters are measured. φ_0L = 0.12 eV is the zero-field ionization energy of a shallow acceptor-type level (measured from the edge of the valence band) which has the dominant effect in the range of 78–230 K. Similarly φ_0H = 0.70 eV corresponds to a deep level dominant in the high-temperature range 230–321 K. In the high-temperature region a 2.7 μm thick hole accumulation layer forms beneath the oxide-gold interface, assuming the ionized deep level is doubly charged.