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

Abstract

InP-based uni-traveling-carrier photodiodes (UTC-PDs) with novel dipole-doped structure to achieve high photocurrent as well as wide bandwidth are demonstrated in this work. 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-µm -diameter top-illuminated UTC-PD is achieved. A large 3-dB bandwidth of 62.5GHz, which is estimated with an equivalent circuit model, has also been obtained from a 12-µm -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 epi-layers growth and device fabrication. Index Terms-Dipole-doped layer, high speed, photocurrent, uni-traveling-carrier photodiodes (UTC-PDs), 3-dB bandwidth. I. INTRODUCTIONIGH-photocurrent and high-speed photodiodes (PDs) have attracted intensive research interests for the application of CATV network, photonic analog-to-digital converter and optical links to phased array antenna [1,2]. To meet the requirements for both high photocurrent and high speed operation, various types of photodiodes have been investigated. Conventional PIN-PD [3] is one of the simplest PD structures which is used for a wide range of applications. In a conventional PIN-PD structure, both electrons and holes are photo-generated in the depletion layer. The holes with much lower drift mobility and velocity, contribute dominantly to the space charge and can result in the degradation of device performance, especially under high power illumination [1].Hence, Ishibashi et al. [1] proposed a new type of photodiode -uni-traveling-carrier photodiode (UTC-PD) which could

Characterization of high‐photocurrent and high‐speed INP‐based uni‐traveling‐carrier photodiodes at 1.55‐μm wavelength

“…A typical InP‐based UTC‐PD consists of a p‐type narrow‐bandgap InGaAs light absorption layer and an n‐type wide‐bandgap InP carrier collection layer . The abrupt energy barrier at InGaAs/InP interface blocking electron flow and causing a buildup of stored charge would degrade DC performance at high current densities and also limit the high‐speed performance of PD.…”

“…The abrupt energy barrier at InGaAs/InP interface blocking electron flow and causing a buildup of stored charge would degrade DC performance at high current densities and also limit the high‐speed performance of PD. To overcome this problem, a dipole‐doped structure, which consists of a p‐type doped 8‐nm InGaAs, a n‐type doped 8‐nm InP layer and a 22‐nm undoped InGaAs setback layer, was inserted between the InGaAs absorption layer and InP collection layer to suppress the current blocking effect . The epi‐layer structure could be found in Table .…”

“…To overcome this problem, a dipole‐doped structure, which consists of a p‐type doped 8‐nm InGaAs, a n‐type doped 8‐nm InP layer and a 22‐nm undoped InGaAs setback layer, was inserted between the InGaAs absorption layer and InP collection layer to suppress the current blocking effect . The epi‐layer structure could be found in Table . The effectiveness of the dipole‐doped structure has been validated by a 3‐dB bandwidth of more than 20 GHz (limited by measurement equipment) and a high‐photocurrent of 160 mA achieved from a 12‐µm‐diameter and a 70‐µm‐diameter fabricated InP‐based dipole‐doped UTC‐PD respectively .…”

“…Uni‐traveling‐carrier photodiodes (UTC‐PDs) with high‐photocurrent and high‐speed performances have been attracting intensive research interests due to their broad applications in high‐performance microwave or millimeter‐wave photonic systems . Recently, we demonstrated that, the InP‐based UTC‐PDs with a novel dipole‐doped structure are able to achieve both a high‐photocurrent and large bandwidth.…”

“…Recently, we demonstrated that, the InP‐based UTC‐PDs with a novel dipole‐doped structure are able to achieve both a high‐photocurrent and large bandwidth. A photocurrent of 160 mA from a 70‐µm‐diameter UTC‐PD and a large 3‐dB bandwidth of 62.5 GHz from a 12‐µm‐diameter UTC‐PD have been realized .…”