| Summary: | 碩士 === 國立成功大學 === 電機工程研究所 === 80 ===
Heterojunction bipolar transistors (HBT's) have been reported and demonstrated to have many advavtages such as high current gain, high cut-off frequency, But the conventional single heterojunction bipolar transistor (SHBT) still has some disadvantages. For example, the conventional SHBT usually exhibits larger offset voltage and the knee- shaped characteristic of the reachthrough effect. In this thesis, the double quantum-well and δ- doped base bipolar transistors have been proposed and investigated.
For the double quantum-well HBT, we pay our attention on the negative defferential resistance (NDR) characteristic and the collector-to-emitter offset voltage Because the sub-emitter and sub-collector are not wide enough to cancel out the depletion regions, the potential spikes at the emitter-base (e-b) and collectorbase (c-d) junctions will exist. The effect of the potential spikes at the e-d and c-d junctions is also a important problem to investigae.
The δ-doped base HBT with a base doping of 2x1013 cm-2 have been fabricated and investigated sucessfully. This device exhibits a common-emitter current gain of 20 and a small collector-to-emitter offset voltage about 60 mV. The knee-shaped characteristic of the reachthrough effect is not found for this device. On the other hand, the base resistance of the δ-doped base HBT is lower than that of the conventional HBT. Then, the high speed performance can be improved. According to above merits, this device is very suitable to the switching application.
|
|---|
