The transistor has four emitter fingers, each finger having dimensions of 3 by 40 pm. The gaps between the emitter and base fingers are approximately 1.5 to 1.75 pm. The size of the bonding pads are approximately 100 by 100 pm. A detailed description of the basic processing parameters of the device can be found in reference 2. Commercial bipolar transistors are made, at the moment, exclusively with Silicon as the semiconductor material, while microwave FETs are mostly fabricated with a Compound semiconductor material, GaAs and AlGaAs. Download chapter PDF References Benjamin, J. A. (1972) New design concepts for microwave power transistors, Microwave Journal 15, 39-64. PDF | The broadband noise performance of silicon ger- manium (SiGe) and compound semiconductor (CS) heterojunc- tion bipolar transistors (HBTs) is presented. The key noise mechanisms in HBTs are summarized to provide a framework through which the noise limitations of the devices can be understood. Process related details and transport physics of each class of device are then compared and Microwave Bipolar Transistor:The micro wave bipolar transistor is a non linear device, which is mostly silicon npn type operating up to '5 GHz'. The geometry of the transistor can be characterized as interdigitated geometry, over lay geometry and matrix geometry. These geometries have wide emitter area to overcome transit time limitations.