ZnO Schottky Nanodiodes Processed From Plasma-Enhanced Atomic Layer Deposition at Near Room Temperature

Abstract

In this paper, we report a low thermal budget manufacturing method to produce highly rectifying Schottky diodes with ultrathin ZnO films grown at near room temperature by plasma-enhanced atomic layer deposition. A bottom Schottky electrode with Pt and a top ohmic electrode with Al/Au stacks were used for metallization. The resultant diodes demonstrated high rectifying ratios on the order of 106, relatively low ideal factor n values of 1.36 ±0.05, effective Schottky barrier height B values of 0.77 ± 0.01 eV, and high breakdown fields of 1.67 MV/cm extrapolated from the current-voltage (I-V) characteristics at room temperature. These specifications are among the best-reported performance of Schottky diodes with ZnO thin films in nanoscale thickness. The interface at the Schottky contacts was investigated and revealed a lateral nonuniform distribution of interface defect states. A modified Richardson plot was used to deduce a mean barrier height (Φ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">B0</sub> ) of 1.25 ± 0.1 eV and an apparent Richardson constantc (A**) of 11.64 A/cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> /K <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> . In addition, I-V characteristics of the diodes were observed to improve with aging. This newly developed, low thermal budget technique of ZnO Schottky nanodiodes is attractive for hybrid circuit systems and polymer electronics with integration constraints.