Design, fabrication, and modeling of indium phosphide double-heterojunction bipolar transistors with sub-millimeter wave cutoff frequency

The compound semiconductor heterojunction bipolar transistor (HBT) is valued today for applications in optoelectronics and high-frequency wireless communications. Though not currently suitable for high-density integration digital logic, these devices are ideal for cutting-edge wireless communication and mixed-signal circuits because of their ability to efficiently generate and amplify high-frequency signals. Developing the high-frequency operation of HBTs to the limits of currently available material systems will bridge the high-power signal generation and detection gap in the electromagnetic spectrum that lies between RF and optical frequencies. This requires advances in semiconductor material design and transistor fabrication to produce active devices with gain in the sub-millimeter wave spectrum above 300 GHz.;The subject of this work is the design and fabrication of heterojunction bipolar transistors based on InP and the III-V compounds compatible with epitaxial growth on this substrate. Scaling and compositional variations of the transistor material layers are studied with the goal of improving device bandwidth. The cutoff frequencies of double-heterojunction transistors are extended as high as 690 GHz while maintaining an off-state breakdown voltage greater than 3 V by using the InP/GaAsSb material system with a type-II energy band alignment. Chapter 1 of this work gives an overview of the relevant materials and device parameters. Material structure design and vertical scaling are discussed in Chapter 2. In Chapter 3, lateral process scaling and the sub-micron HBT fabrication process are presented. Chapter 4 details the material designs studied and the measured device results including sub-micron HBTs with record RF performance. Chapter 5 presents small-signal parameter extraction and modeling work. Future work in device design and fabrication is proposed in Chapter 6.