Enhanced Electrical Properties of Optimized Vertical Graphene-Base Hot Electron Transistors

The arrival of high-mobility two-dimensional materials like graphene leads to the renaissance of former vertical semiconductor- metal-semiconductor (SMS) hot electron transistors. Because of the monolayer thickness of graphene, improved SMS transistors with a semimetallic graphene-base electrode are now feasible for high-frequency applications. In this study we report about a device that consists of amorphous silicon, graphene, and crystalline silicon. For the first time, this device is fabricated by a four-mask lithography process which leads to significant improvements in the device performance. A strongly increased common-emitter current gain of 2% could be achieved while the on-off ratio improved to 1.6 x 105, which is already higher than predicted theoretically. This could be mainly attributed to better interface characteristics and decreased lateral dimensions of the devices. A cutoff frequency of approximately 26 MHz could be forecasted based on the DC measurements of the device.

Automated summary

The arrival of high-mobility two-dimensional materials like graphene has brought back the vertical semiconductor-metal-semiconductor (SMS) hot electron transistors. With the monolayer thickness of graphene, improved SMS transistors with a semimetallic graphene-base electrode are now possible for high-frequency applications. In this study, a device composed of amorphous silicon, graphene, and crystalline silicon is reported. The device is fabricated by a four-mask lithography process for the first time, leading to significant improvements in device performance. A strongly increased common-emitter current gain of 2% has been achieved, while the on-off ratio improved to 1.6 x 105, surpassing theoretical predictions. Better interface characteristics and decreased lateral dimensions of the devices were the main contributing factors. Based on DC measurements, a cutoff frequency of approximately 26 MHz is expected.