Analytical relations pertaining to collector current density and base transit time in bipolar transistors

1996 ◽  
Vol 39 (1) ◽  
pp. 173-175 ◽  
Author(s):  
Pingxi Ma ◽  
Lichun Zhang ◽  
Yangyuan Wang
Keyword(s):  
Transit Time ◽  
Current Density ◽  
Bipolar Transistors ◽  
Collector Current ◽  
Analytical Relations

Current Gain of 4H-SiC Bipolar Transistors Including the Effect of Interface States

2005 ◽  
Vol 483-485 ◽  
pp. 889-892 ◽  
Author(s):  
Martin Domeij ◽  
Erik Danielsson ◽  
Hyung Seok Lee ◽  
Carl Mikael Zetterling ◽  
Mikael Östling
Keyword(s):  
Side Wall ◽  
Interface States ◽  
Bipolar Transistors ◽  
Current Gain ◽  
Poor Agreement ◽  
Collector Current ◽  
Bandgap Narrowing ◽  
Pulsed Measurements ◽  
Emitter Junction ◽  
Constant Distribution

The current gain (b) of 4H-SiC BJTs as function of collector current (IC) has been investigated by DC and pulsed measurements and by device simulations. A measured monotonic increase of b with IC agrees well with simulations using a constant distribution of interface states at the 4H-SiC/SiO2 interface along the etched side-wall of the base-emitter junction. Simulations using only bulk recombination, on the other hand, are in poor agreement with the measurements. The interface states degrade the simulated current gain by combined effects of localized recombination and trapped charge that influence the surface potential. Additionally, bandgap narrowing has a significant impact by reducing the peak current gain by about 50 % in simulations.

scholarly journals Study on Possible Double Peaks in Cutoff Frequency Characteristics of AlGaAs/GaAs HBTs by Energy Transport Simulation

VLSI Design ◽  
1998 ◽  
Vol 8 (1-4) ◽  
pp. 437-442
Author(s):  
T. Okada ◽  
K. Horio
Keyword(s):  
Heterojunction Bipolar Transistors ◽  
Energy Transport ◽  
Transport Model ◽  
Cutoff Frequency ◽  
Bipolar Transistors ◽  
Electron Velocity ◽  
Collector Current ◽  
Double Peak ◽  
Double Peaks ◽  
Energy Profiles

By using an energy transport model, we simulate cutoff frequency fT  versus collector current density IC characteristics of npn−n AlGaAs/GaAs heterojunction bipolar transistors (HBTs) with various n−-collector thickness and n−-doping densities. It is found that the calculated fT  characteristics show double peak behavior when the n−- layer is thick enough and the n−-doping is high enough to allow existence of neutral n−- region. The mechanism of the double peak behavior is discussed by studying energy band diagrams, electron-energy profiles and electron-velocity profiles. Particularly, we discuss the origin of the second peak (at higher IC) which is not usually reported experimentally.

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