www.tjprc.org editor@tjprc.org COMPARATIVE STUDY ON FREQUENCY RESPONSE OF HETEROJUNCTION BIPOLAR TRANSISTOR ARNIMA DAS & MAITREYI RAY KANJILAL Department of Electronics and Communication Engineering, Narula Institute of Technology, Kolkata, West Bengal, India ABSTRACT The performance of RF devices are assessed through Figure of Merit which provide certain quantitative idea about the RF device. Hetero-junction transistors are being used over a high radio frequency range up to several hundred GHz. The performance of these transistors can also be assessed using some key factors like Stability and Power gain. In the present paper Si/SiGe and AlGaAs/GaAs HBTs are simulated over a significant portion of High radio frequency range up to 1 THz suitable for application in wireless and satellite communication. The analysis has been made on both HBTs looking at future prospective. KEYWORDS: Hetero-Junction Bipolar Transistor, Figure of Merit, Rollett’s Stability Factor, Maximum Available Gain, Maxi-Mum Stable Gain, Critical Frequency Received: Jul 24, 2016; Accepted: Aug 22, 2016; Published: Aug 24, 2016; Paper Id.: IJEEEROCT20161 INTRODUCTION Radio Frequency (RF) electronics with RF transistors have been a major field of study and invention, but it went unnoticed till 1980 as most of the work in this field was related to military projects or other exotic science projects. The introduction of mobile communication and satellite communication for the civil purpose has garnered increased attention towards the development of RF electronics. The new communication systems of the 21 st century transmit, process and receive a great amount of data in the GHz frequency range and the RF transistors are the backbone of this high frequency communication system. This system encompasses RF frequency ranges from Ultra High Frequency (UHF – up to 3 GHz) to Tremendously High Frequency (THF – up to 3 THz). The increasing frequency range of RF communication system has brought a massive growth in the study of high frequency transistors which are mostly hetero-junction transistors, such as the Hetero-junction Bipolar Transistor (HBT) and the High Electron Mobility transistor (HEMT). Although Field effect transistors have shown much broader range of capabilities, while the junction transistors are valued for their smaller footprint per unit current gain. Also Bipolar Transistor shows higher transconductance and sub-micron base width can be realized, which is independent of photolithography. The Hetero-junction Bipolar Transistor is a type of Junction transistor, which uses different semiconductor materials for the emitter and base regions. Thus, creating an emitter-base hetero-junction and in some cases also a base-collector hetero-junction. Since, in a hetero-junction the potential barrier in valence band is higher than that of conduction band, so, this limits the injection of holes or electrons from base to emitter. This allows high doping density to be used in the base region, which reduces the base resistance, maintaining Original Article International Journal of Electrical and Electronics Engineering Research (IJEEER) ISSN(P): 2250-155X; ISSN(E): 2278-943X Vol. 6, Issue 5, Oct 2016, 1-6 © TJPRC Pvt. Ltd.