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的垂直晶体管概念。石墨烯被用作极薄、低电阻率的基极。石墨烯基区异质结晶体管(GBHT)可以看作是一种NPN双极型晶体管，其p型基区被石墨烯层所取代。这一新颖的概念是基于发射极、基极和集电极的垂直排列。该器件由一个n型半导体(发射极)、一个石墨烯单层(基区)和另一个n型半导体(集电极)堆叠而成，在上一个项目(DFG BA 2009/6-1和WE3594/5-1)的提案中已经详细解释了这种新的晶体管概念的能带结构、工作原理和其他优点。在所提出的n型氢化非晶硅(a-Si：H)柔性衬底上的晶体管配置中，频率高达100 GHz应该是可行的，因为截止频率主要由a-Si：H的迁移率控制。据我们所知，到目前为止，我们是世界上唯一一个致力于这一有前途的独特器件概念的团队。这项开创性的工作可能会为使用石墨烯的新型电子设备铺平道路。接收器和传输电路是无线通信的基本元素。根据模拟结果，高频振荡器可以被设想为第一个应用。利用a-Si：H/石墨烯二极管的可变电容，可以集成一个变容二极管来实现压控振荡器的设计。这种方法可以在柔性衬底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.