United States Army Research Laboratories, Sensors and Electron Devices Directorate, 2800 Powder Mill Road, Adelphi, Maryland 20783, USA.
Department of Materials Science and NanoEngineering, Rice University, Houston, Texas 77005, USA.
Sci Rep. 2016 Dec 20;6:39465. doi: 10.1038/srep39465.
The interfaces in devices made of two-dimensional materials such as MoS can effectively control their optoelectronic performance. However, the extent and nature of these deterministic interactions are not fully understood. Here, we investigate the role of substrate interfaces on the photodetector properties of MoS devices by studying its photocurrent properties on both SiO and self-assembled monolayer-modified substrates. Results indicate that while the photoresponsivity of the devices can be enhanced through control of device interfaces, response times are moderately compromised. We attribute this trade-off to the changes in the electrical contact resistance at the device metal-semiconductor interface. We demonstrate that the formation of charge carrier traps at the interface can dominate the device photoresponse properties. The capture and emission rates of deeply trapped charge carriers in the substrate-semiconductor-metal regions are strongly influenced by exposure to light and can dynamically dope the contact regions and thus perturb the photodetector properties. As a result, interface-modified photodetectors have significantly lower dark-currents and higher on-currents. Through appropriate interfacial design, a record high device responsivity of 4.5 × 10 A/W at 7 V is achieved, indicative of the large signal gain in the devices and exemplifying an important design strategy that enables highly responsive two-dimensional photodetectors.
二维材料（如 MoS）制成的设备中的界面可以有效地控制其光电性能。然而，这些确定性相互作用的程度和性质还不完全清楚。在这里，我们通过研究其在 SiO2 和自组装单层修饰基底上的光电流特性，研究了基底界面对 MoS 器件光电探测器性能的作用。结果表明，虽然通过控制器件界面可以提高器件的光响应度，但响应时间会适度降低。我们将这种折衷归因于器件金属-半导体界面处的接触电阻的变化。我们证明，在界面处形成的载流子陷阱可以主导器件的光电响应特性。深陷阱载流子在基底-半导体-金属区域中的俘获和发射速率受光照射的强烈影响，并且可以动态地掺杂接触区域，从而干扰光电探测器的性能。因此，经过界面修饰的光电探测器具有显著更低的暗电流和更高的导通电流。通过适当的界面设计，在 7V 时实现了创纪录的 4.5×10 A/W 的器件响应率，这表明器件中有大信号增益，例证了一种重要的设计策略，该策略可以实现高响应的二维光电探测器。
