The Transient Effect of Current Gain in InGaP/GaAs HBTs

• Main Authors: Shr-Ting Lin, 林世庭
• Other Authors: Yeong-Her Wang
• Format: Others
• Language: en_US
• Published: 2002
• Online Access: http://ndltd.ncl.edu.tw/handle/26053818418328304065

碩士 === 國立成功大學 === 微電子工程研究所碩博士班 === 90 === With the development of the wireless communication, microwave devices play a very important role; the heterojunction bipolar transistors are the devices currently of the power amplifiers in RF-IC circuit. By the selectivity of the heterostructure material, InGaP/GaAs have replaced AlGaAs/GaAs because of it’s better structure of band gap and characteristics. In this thesis, we use the same masks to accomplish the normal structure and self-aligned structure InGaP/GaAs HBTs. The self-aligned technology reduced the emitter-base space from 10um to within 1um. HBT with smaller extrinsic base area, which decrease the surface recombination current and obtain the larger current gain. In our device, the current gain will increase gradually, which is called transient effect, when we give the HBT a fixed bias. We changed the space between emitter and base, observed the emitter size effect of HBT, and some electric measurement to identify the reason of the transient effect; moreover, we used several voltage stress conditions to find the optimum condition to annihilate the transient effect. We also treated the devices with thermal annealing to improve the transient effect. The transient effect can not be annihilated by annealing because the device can’t tolerate the temperature that is too high(>600℃), but the thermal annealing at 550℃ can decrease the interval of transient effect and annihilate the reproducible phenomenon when device followed a voltage stress to annihilate the transient effect. Finally, we obtain the characteristics of HBT with current gain ~ 120, the offset voltage ~ 100mV, turn-on voltage ~ 1.14V, and break down voltage ~ 15V.