Department of Electrical Engineering and Computer Science, University of Michigan , Ann Arbor, Michigan 48109-2122, United States.
ACS Appl Mater Interfaces. 2016 Sep 14;8(36):23801-9. doi: 10.1021/acsami.6b05953. Epub 2016 Sep 1.
Here we present a novel in situ chemical modification process to form vertical Schottky diodes using palladium (Pd) rectifying bottom contacts, amorphous zinc tin oxide (Zn-Sn-O) semiconductor made via acetate-based solution process, and molybdenum top ohmic contacts. Using X-ray photoelectron spectroscopy depth profiling, we show that oxygen plasma treatment of Pd creates a PdOx interface layer, which is then reduced back to metallic Pd by in situ reactions during Zn-Sn-O film annealing. The plasma treatment ensures an oxygen-rich environment in the semiconductor near the Schottky barrier, reducing the level of oxygen-deficiency-related defects and improving the rectifying contact. Using this process, we achieve diodes with high forward current density exceeding 10(3)A cm(-2) at 1 V, rectification ratios of >10(2), and ideality factors of around 1.9. The measured diode current-voltage characteristics are compared to numerical simulations of thermionic field emission with sub-bandgap states in the semiconductor, which we attribute to spatial variations in metal stoichiometry of amorphous Zn-Sn-O. To the best of our knowledge, this is the first demonstration of vertical Schottky diodes using solution-processed amorphous metal oxide semiconductor. Furthermore, the in situ chemical modification method developed here can be adapted to tune interface properties in many other oxide devices.
在这里，我们提出了一种新颖的原位化学修饰工艺，使用钯（Pd）整流底接触、通过基于醋酸盐的溶液工艺制备的非晶态锌锡氧化物（Zn-Sn-O）半导体以及钼顶欧姆接触，形成垂直肖特基二极管。通过 X 射线光电子能谱深度剖析，我们表明氧等离子体处理 Pd 会在肖特基势垒附近的半导体中形成 PdOx 界面层，然后在 Zn-Sn-O 薄膜退火过程中的原位反应中将其还原回金属 Pd。等离子体处理确保了肖特基势垒附近半导体中的富氧环境，减少了与氧空位相关缺陷的水平，从而改善了整流接触。使用该工艺，我们实现了在 1V 时正向电流密度超过 10(3)A cm(-2)、整流比>10(2)和理想因子约为 1.9 的二极管。测量的二极管电流-电压特性与半导体中热电子场发射和亚带隙状态的数值模拟进行了比较，我们将其归因于非晶态 Zn-Sn-O 的金属化学计量比的空间变化。据我们所知，这是首次使用溶液处理的非晶态金属氧化物半导体演示垂直肖特基二极管。此外，这里开发的原位化学修饰方法可以适应许多其他氧化物器件中界面性质的调整。
