Abstract :
Research and development activities in Japan for microwave and millimeterwave HBT´s are reviewed. Selective p+-GaAs regrowth techniques, and a Pt/Ti/Pt/Au contact metal sysem are effective for improving maximum oscillation frequency, fmax. Ballistic collection transistor (BCT) structures significantly reduce collector transit time resulting in high current gain cutoff frequency, fT, and fmax More than 200-GHz fmax is achieved. For power applications, reducing thermal resistance is necessary for achieve highly efficient, high power operations. An effective bump heat sink(BHS) structure is demonstrated, delivering 5W power output with 74 % power added efficiency. Recent results are described for power output performances from discrete HBTs, an MMIC amplifier requiring only 1.5 V power supply for digital cordless phone systems, DC-18.5 GHz broadband transimpedance amplifiers for optical communications, low phase noise oscillators, and ultra high speed digital IC´s operating at over 40Gbps.
