First high-frequency and power demonstration of InGaAlAs/GaAsSb/InP double HBTs

InGaAlAs/GaAsSb/InP Double HBTs with micrometer emitter size were designed, processed and characterized with DC, microwave and power performance for the first time. In addition to the advantages of using type-II band line-up at base-collector junction, the DHBT structure results in small turn-on voltage and ballistic launching of electrons due to the positive conduction band discontinuity from the emitter to base. Fabricated large DHBTs showed high DC gain (>80), small turn-on voltage of 0.62V, almost zero offset voltage, and nearly ideal base and collector current characteristics. Small DHBTs demonstrated V/sub CEO/ >8V and stable operation at high current density exceeding 100kA/cm/sup 2/. Maximum f/sub T/ of 57GHz and maximum f/sub max/ of 66GHz were achieved from 1/spl times/20/spl mu/m/sup 2/ device at J/sub C/ = 8.0/spl times/10/sup 4/ A/cm/sup 2/ and V/sub CE/ =3.5V. Preliminary power measurement of 2/spl times/15/spl mu/m/sup 2/ device showed a linear gain of 10dB and compressed output power of 5dBm at 5GHz.