Flexible Graphene-Base Heterojunction Transistor for Several Hundred Gigahertz Operation

在这个项目中，我们将研究一种在柔性衬底上制造的新型垂直晶体管概念。石墨烯被用作极薄、低电阻率的基电极。石墨烯基异质结晶体管（GBHT）可以被认为是一个p型基被石墨烯层取代的NPN双极晶体管。这个新颖的概念是基于发射极、基极和集电极的垂直排列。该器件由n型半导体（发射极）、石墨烯单层（基底）和另一种n型半导体（集电极）堆叠而成。在之前的项目提案（DFG BA 2009/6-1和WE3594/5-1）中详细解释了这种新型晶体管概念的频带方案、工作原理和附加优点。在柔性衬底上采用n型氢化非晶硅（a-Si:H）的晶体管结构中，由于截止频率主要由a-Si:H的迁移率控制，高达100 GHz的频率应该是可行的。据我们所知，我们是迄今为止全球唯一致力于这一有前途的独特设备概念的团队。这项开创性的工作将有可能为石墨烯的新一类电子设备铺平道路。接收和传输电路是无线通信的基本组成部分。基于仿真结果，可以设想高频振荡器作为第一个应用。利用a- si:H /石墨烯二极管的可变电容，可以集成一个变容管器件来实现作为电压控制振荡器的设计。这种方法可以在柔性基板上实现第一个构建块。

In this project we will investigate a new vertical transistor concept fabricated on flexible substrates. Graphene is used as an extremely thin, low resistivity base electrode. The graphene base heterojunction transistor (GBHT) can be thought of as a NPN bipolar transistor with the p-type base being replaced by a graphene layer. This novel concept is based on a vertical arrangement of emitter, base, and collector. The device is obtained by stacking an n-type semiconductor (emitter), a graphene monolayer (base), and another n-type semiconductor (collector).The band scheme, working principle and additional advantages of this novel transistor concept have been explained in detail in the proposal of the previous project (DFG BA 2009/6-1 and WE3594/5-1). In the proposed transistor configuration on flexible substrates with n-type hydrogenated amorphous silicon (a-Si:H), frequencies up to several 100 GHz should be feasible, because the cut-off frequency is mainly controlled by the mobility of a-Si:H. To our knowledge, we are the only group worldwide so far working on this promising unique device concept. This pioneering work will potentially pave the way for a new class of electronic devices with graphene in general.The receiver and transmission circuits are the fundamental elements of wireless communications. Based on simulation results, a high frequency oscillator can be envisioned as a first application. Using the variable capacitance of the a-Si:H / graphene diodes, a varactor device could be integrated to implement the design as a voltage controlled oscillator. This approach could enable the first building block on flexible substrates.