Until now, a common feature of many wide band gap heterojunction diodes is an unexplained large ideality factor . In this context we investigate the diode characteristics of heterojunction diodes consisting of a crystalline semiconductor material such as ZnO covered with a thin semiconducting film of amorphous or disordered material. As thin disordered film we use -bonded turbostratic boron nitride. These heterojunctions exhibit a pronounced rectifying behavior, low saturation current, and low parasitic currents. Moreover, we observe an apparently giant ideality factor reaching values of . As a consequence, the turn-on voltage is around 5–10 V and the curves can be measured for bias voltages between ±80 V without reaching saturation or electrical breakdown. We present a quantitative model for the unusual diode characteristics of these metal-amorphous semiconductor-semiconductor diodes. We demonstrate that the characteristics of the heterojunctions are well described by a serial arrangement of an ideal Schottky diode, a Frenkel–Poole type resistance, and an Ohmic contact resistance, emulating a - or Schottky diode characteristic with giant ideality factor. We propose that heterojunctions exhibiting apparently large ideality factors may possess an interfacial disordered or amorphous layer with Frenkel–Poole conduction properties.
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Research Article| September 18 2009
BN/ZnO heterojunction diodes with apparently giant ideality factors
M. Brötzmann, U. Vetter, H. Hofsäss; BN/ZnO heterojunction diodes with apparently giant ideality factors. J. Appl. Phys. 15 September 2009; 106 (6): 063704. https://doi.org/10.1063/1.3212987
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