Bipolar transistors current gain

Huang, C. -F, and J. A. Cooper, Jr., 4H-SiC Power Bipolar Transistors with Common Emitter Current Gain > 50, Technical Digest of the Device Research Conference 2002, Santa Barbara, CA, June 2002, pp. 183-184. 

Zhang, J., et al., A High Current Gain 4H-SiC NPN Power Bipolar Junction Transistor, IEEE Electron Device Letters, Vol. 24, No. 5, May 2003, pp. 327-329. 

Tang, Y., J. B. Fedison, and T. P. Chow, An Implanted-Emitter 4H-SiC Bipolar Transistor with High Current Gain, Technical Digest of 58th Device Research Conference, Denver, CO, June 19-21, 2000, pp. 131-132. 

In this section we will investigate how the DC current gain (Hfe) of a bipolar junction transistor varies with DC bias collector current Icq, DC bias collector-emitter voltage Vceq, and temperature. We will use the basic circuit shown below for all simulations ... 

Compared with a conventional bipolar transistor, the tunnel collector efficiency is low and this means the collector base current gain, is modest for such transistors. This current is determined not just by base recombination as is usual in standard transistors but also by the fraction of carriers that evade the collection process. Another unusual feature is the form of the output admittance, which is determined by the upper band structure of the ferromagnetic collector material and the effective tunnel barrier width. It is therefore non-negligible and is predictably a function of Vce. 

The first work that utilized a bipolar transistor was that of Prins (52). Using a natural p-type diamond bulk crystal as a substrate, carbon ions are ion implanted to form n-type-like regions with 3.2-pm-diameter wire as a implant mask. The energy level and mechanism of the carbon implantation cannot be estimated however, bipolar transistor behavior was achieved. The I-V characteristics are shown in Fig. 9. Although the current gain of ftp = Ic/h is only 0.11, the impact on researchers in this field was not insignificant. This was followed by several research activities, such as work on npn bipolar transistors with As implanted n-type-like regions and a point contact bipolar-like transistor (53). 

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