Circuit Modeling of Tunneling Real-Space Transfer Transistors: Toward   Terahertz Frequency Operation
  High frequency operation of tunneling real-space transfer transistor (TRSTT) in the negative differential resistance (NDR) regime is assessed by calculating the device common source unity current gain frequency (fT) range with a small signal equivalent circuit model including tunneling. Our circuit model is based on an In0.2Ga0.8As and delta-doped GaAs dual channel structure with various gate lengths. The calculated TRSTT fT agrees very well with experimental data, limiting factor being the resistance of the delta-doped GaAs layer. By optimizing the gate dimensions and channel materials, we find fT in the NDR region approaches terahertz range, which anticipates potential use of TRSTT as terahertz sources. 
Wen Huang, Xin Yu, Shi-Lin Zhang, Lu-Hong Mao, and Jean-Pierre   Leburton
cond-mat.mes-hall cond-mat.mtrl-sci