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Figure 1. (a) The schematic of one conceivable GBT device; (b)Cross section of on GBT device. (c) The energy band diagram of the GBT under zero bias; and (d) the energy band diagram of a GBT in the ON state [5].

References:

  1. L. Britnell, R. V. Gorbachev, R. Jalil, B. D. Belle, F. Schedin, A. Mishchenko, T. Georgiou, M. I. Katsnelson, L. Eaves, S. V. Morozov, N. M. R. Peres, J. Leist, A. K. Geim, K. S. Novoselov, and L. A. Ponomarenko. Field-Effect Tunneling Transistor Based on Vertical Graphene Heterostructures. Science, 335, 947 (2012).
  2. W. H. Eccles, Triode Valves as Electric Amplifiers. Nature, 104, 501 (1920).
  3. C. A. MEAD. Operation of Tunnel-Emission Devices. Journal of Applied Physics. 32, 646 (1961).
  4. Herbert Kroemer. Heterostructure Bipolar Transistors and Integrated Circuits. Proceedings of the IEEE, 70, 13 (1982).
  5. Wolfgang Mehr, Jarek Dabrowski, J. Christoph Scheytt, Gunther Lippert, Ya-Hong Xie, Max C. Lemme, Mikael Ostling, and Grzegorz Lupina. Vertical Graphene Base Transistor. Electron Device Letters, 33, 691 (2012).

Semiconductor Materials Research Laboratory, Department of Materials Science and Engineering, University of California, Los Angeles

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Graphene Base Transistor

 

One of our research interests pertains to the transport of out-of-plane electrons through graphene with graphene base transistors (GBT) as the specific device embodiment [1]. For energetic electrons, the probability of them thermalizing (thereby getting trapped) in graphene is nearly prohibited by quantum mechanical selection rules leading to an array of the anticipated interesting device possibilities.

Figure 1a & 1b show the schematics of a GBT with the associated energy band diagram.  The device physics of GBTs straddles that of triodes (a three-terminal vacuum tube transistor) [2], hot-electron transistor (HET) [3], and that of bipolar junction transistors (BJTs) [4] with distinctive advantages over all three families of transistors. In some senses, GBTs can be thought of as the nanometer version of triodes without the hot filaments and the HETs and BJTs with an atomic layer thick base. As such, there are a number of the anticipated performance advantages including exceedingly high current gain, negligibly small Early effect, and high fT. Figure 2 shows the simulated output characteristics and the fT-V curve [5]. Figure 3 shows a typical emitter-base I-V characteristic.

Our research aim at deepen the fundamental understanding of the physics governing the graphene-energetic electrons interaction. Our research is expected to lead to novel devices leveraging this unique aspect of graphene.

The research will expose the students/participants to the exciting world of van der Waals materials such as graphene. The participants will have the opportunity to gain in-depth knowledge of transistors while acquiring hands-on experience in device fabrication and characterization.

 

 

 

 

 

 

 

 

 

 

 

Figure 2. The simulated output characteristics (c), and fT-V curve (d) of GBT [5].

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Figure 3. Current-voltage (I-V) characteristic of the forward and reverse biased emitter-base junction diode with Si emitter and graphene base.