An InP-based InGaAs/AlAs/InAs resonant tunneling diode (RTD) and a uni-traveling-carrier photodiode (UTC-PD) are monolithically integrated by the regrowth technique to utilize the excellent device characteristics of the RTD and the UTC-PD. The RTD structures are regrown by molecular beam epitaxy on the top of UTC-PD structures grown by metalorganic chemical vapor deposition. The characteristics of the regrown RTDs are almost the same as those of conventional RTDs grown on semi-insulating InP substrates. The UTC-PD provides a sufficient current drivability, shown by the responsivity of 0.27 A/W, along with a high-speed operation demonstrated by the -3-dB bandwidth of 80 GHz, even at the low bias voltage corresponding to the peak voltage of the RTD. A simple circuit configuration of an optoelectronic logic gate with two RTDs and one UTC-PD was fabricated. This optoelectronic logic gate exhibited proper delayed flip-flop operation of 40 gbit/s at 7.75 mW. These results suggest that a circuit using RTDs and a UTC-PD is suitable for the construction of ultrahigh-speed and low-power optoelectronic circuits.
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