Wide bandwidth power heterojunction bipolar transistors and amplifiers

Wide bandwidth power hetero-junction bipolar transistors (HBT) fabricated in a transferred-substrate technology have been developed, which exhibit 330 GHz power gain cut-off frequency at 100 mA collector current and 3.6V collector-emitter voltage. The collector-emitter breakdown voltage is 7V. These power HBTs were realized in a multiple finger topology that substantially reduces the base-collector parasitic capacitance, which typically limits the bandwidth of power HBTs. While thermal effects may be of concern in small area HBT design, the thermo-electric feedback effects are much more complex and significant in large-area devices. Methods of characterizing electrical and thermal properties of multiple finger HBTs are demonstrated and approaches for improving both their bandwidth and power performance are presented. AN HBT large-signal model is developed based on device electrical and thermal characterization. The model demonstrates accurate agreement with measurement data and has been used in power amplifier design. W-band (75 GHz to 110GHz) monolithic integrated circuit (MIC) power amplifiers with transferred-substrate power HBTs have been developed. Amplifier results include 40 mW saturated output power at 85 GHz and 80 mW saturated output power at 75 GHz. These are the highest output power reported in HBT technology at these frequencies. A V-band power amplifier using the same technology was also developed and demonstrates output power of 80mW at 40 GHz with 1-dB gain-compression.; A millimeter-wave air dipole antenna fabrication technology was developed to enable the development of high efficiency 94 GHz quasi-optical arrays. The process is compatible with the transferred-substrate HBT monolithic microwave integrated circuit technology. By using quasi-optical power combining technique, the output power of numerous W-band power amplifiers can be combined in the free space to achieve high-power amplifiers.