High-Photocurrent and Wide-Bandwidth UTC Photodiodes With Dipole-Doped Structure

InP-based unitraveling-carrier photodiodes (UTC-PDs) with novel dipole-doped structure to achieve high photocurrent as well as wide bandwidth are demonstrated in this letter. The dipole-doped layers in combination with a 22-nm-thick undoped InGaAs setback layer were employed at the InGaAs/InP absorption and collection interface to reduce the current blocking effect. A high photocurrent of 160 mA with 1.9 GHz 3-dB bandwidth from a 70-(mu ) m-diameter top-illuminated UTC-PD is achieved. A large 3-dB bandwidth of 62.5 GHz, extracted using an equivalent circuit model, has also been obtained from a 12-(mu ) m-diameter UTC-PD device. The results demonstrate that the dipole-doping can serve as an effective alternative to the quaternary InGaAsP layer at InGaAs/InP interface for InP-based UTC-PD to suppress the current blocking and reduce the complexity in epilayers growth and device fabrication.