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Title:Current Blocking in Type-I DHBTs
Author(s):Bambery, Rohan
Contributor(s):Feng, Milton
Subject(s):current blocking
bipolar transistors
double-heterojunction bipolar transistors
type I double-heterojunction bipolar transistors
Kirk effect
Abstract:The phenomenon of current blocking sets the I-V characteristic of heterojunction bipolar transistors apart from their homojunction counterparts. The effect stems from the triangular quantum well energy spike at the base collector junction of the DHBT. The theory governing the effect is discussed using energy band diagrams and potential barriers at the junctions under different DC bias conditions. Current blocking is predicted to be dominant under low bias. This effect decreases at higher bias since the spike is pulled down at the C-B junction. Three Type - I InP/InGaAs/InP DHBTs of different sizes were tested using a 20-μA base current stepping and maximum DC bias VC = 1V. Each of the devices exhibited the classic bowing in the I-V curve which is characteristic of current blocking. These measurements are discussed along with a comparison of the effects of device size on the phenomenon. The results clearly show current blocking under low DC bias and a relative decrease in the effect at a higher VC. The use of Type –II DHBTs effectively overcomes the problem of tunneling through the conduction band spike, and exhibits very little current blocking. The dominant effect in Type –II devices is base push-out or the Kirk Effect. This is discussed in brief along with measurements showing the improvement in the I-V characteristic.
Issue Date:2008-05
Publication Status:unpublished
Peer Reviewed:not peer reviewed
Date Available in IDEALS:2014-01-27

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