High bandwidth surface-illuminated InGaAs/InP uni-travelling-carrier photodetector

Abstract

Uni-traveling-carrier photodiodes (UTC-PDs) with ultrafast response and high saturation output are reported. A gradient doping layer and a narrow InP cliff layer were introduced to enhance the saturation and bandwidth characteristics. We measured the dark current, photo response, bandwidth, and saturation current of the fabricated UTC devices. For a 15-µm-diameter device, the dark current was 3.5 nA at a reverse bias of 1 V, and the 3-dB bandwidth was 17.2 GHz at a reverse bias of 5 V, which are comparable to the theoretically values. The maximum responsivity at 1.55 µm was 0.32 A/W. The saturation output current was over 19.0 mA without bias.

Bandwidth improvement of high power uni-traveling-carrier photodiodes by reducing the series resistance and capacitance

“…Compared with the conventional pin PDs, [3] the UTC structure is composed of a heavily doped pregion and an undoped depletion region, in which the holes are collected by the p-electrode with a short relaxation time and only the electrons drift in the depletion region, thus greatly enhancing the bandwidth and output RF power due to the higher velocity of electrons relative to that of holes. [4] The modified uni-traveling carrier photodiode (MUTC-PD) is developed by inserting an undoped InGaAs layer between the heavily doped absorption region and the depletion region of the UTC structure to increase the responsivity and bandwidth, [5] and it is also an important candidate to achieve a wide bandwidth and high saturation performance simultaneously.…”

Design guidelines for edge‐coupled waveguide unitravelling carrier photodiodes with improved bandwidth

“…8b shows the calculated impact of the absorber layer doping concentration on the bandwidth of the UTC PD. It has been proposed [19,20] that introducing step-like and gradient doping concentration profiles in the absorber layer lead to a speed up of electron diffusion towards the collector layer by forming a quasi-neutral electric field, which improves carrier transport [3]. Here we compare a constant doping concentration (1 × 10 19 cm −3 ) with graded doping concentrations in the absorber layer of the UTC PD.…”

Effects of Interface States on Ge-On-SOI Photodiodes

“…Additionally, because of the lower Ge bandgap, the generation-recombination current governed by the Shockley-Read-Hall (SRH) process (J SRH ) in Si/Ge photodiodes is higher than that in III-V photodetectors [22], [23]. Therefore, the dark current in a vertical p+(Ge)-i(Ge)-n+(Si) photodiode (44.1 mA/cm 2 ) is significantly higher than that in commercial III-V photodetectors (15.2 µA/cm 2 ) [24]. However, there have been no reports to date of determination of the major noise source or consideration of the effects of interface states on the responsivity and 3-dB bandwidth of Si/Ge photodetectors.…”