| The InP/GaAsSb/InP DHBT (Double Heterojunction Bipolar Transistor) has demonstrated superior high-frequency performance and is attractive for next generation's microwave electronics due to its inherently low bandgap base material GaAsSb, high electron speed in collector material InP, and type-II band lineup at the base-collector heterojunction. This work studied the GaAsSb material properties, advanced the InP-based GaAsSb DHBT device technology, and developed related high-speed/high-power microwave integrated circuits for the first time.; The material study of this work focused on proper characterizations of GaAsSb material and GaAsSb DHBT device structures. Various techniques using photoluminescence, X-ray diffraction, low-angel incident X-ray refraction, and Hall measurement were deployed. The device study focused on implementing a reliable fabrication process flow of GaAsSb DHBT devices, and characterizing the devices in terms of power gain, output compression, and circuit matching properties. Novel self-aligned emitter etch steps were proposed and resulted in uniform device topology and performance. InP/GaAsSb/InP DHBT devices with 1x10mum2 emitter-size demonstrated a maximum fT of 132GHz and fmax of 105GHz. Microwave power density as high as 1.9mW/mum2 at 5GHz was also demonstrated and confirmed the suitability of GaAsSb DHBTs in simultaneous high-frequency and high-power circuit applications. The first-generation low-power/low-noise transimpedance amplifiers with the state-of-the-art performance were demonstrated. The first InP/GaAsSb/InP DHBT MMIC (Monolithic Microwave Integrated Circuit) oscillator at Ka-band was also developed in this work.; Future studies on GaAsSb material growth will be continued using additional characterization techniques. Device process optimizations, DC gain degradation at emitter-base junction, and scalable small-signal/large-signal device models will be addressed. Finally, further improvement and explorations of various high-speed/high-power MMICs are expected using InP-based GaAsSb DHBT devices. |
