We have investigated manufacturability of InP DHBTs for the applications to 40 Gbit/s optical communications ICs. Our DHBTs feature a carbon-doped InGaAs base and an InGaAs/InGAsP/InP step-graded collector with its conduction-band potential profile properly controlled by the doping dipole. The fabricated transistors yield current gain of 30, collector breakdown voltage, BV{sub}(CEO), of over 8V, and ideal current turn-on behavior up to 1 mA/μm{sup}2. Sixty-eight transistors on a 3" substrate exhibit f of 131 ± 2 GHz and f{sub}(max) of 191 ± 15 GHz under the bias conditions of V{sub}(CE) 1.2V and J{sub}C 0.5 mA/μm{sup}2. We also fabricated 1/2 static frequency divider ICs with ECL gates configuration and confirmed maximum operation frequency of over 40 GHz. This value is by no means inferior to that of dividers fabricated with conventional SHBTs.
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