High-responsivity vertical-illumination Si/Ge uni-traveling-carrier photodiodes based on silicon-on-insulator substrate

Abstract

Si/Ge uni-traveling carrier photodiodes exhibit higher output current when space-charge effect is overcome and the thermal effects is suppressed. High current is beneficial for increasing the dynamic range of various microwave photonic systems and simplifying high-bit-rate digital receivers in many applications. From the point of view of packaging, detectors with vertical-illumination configuration can be easily handled by pick-and-place tools and are a popular choice for making photo-receiver modules. However, vertical-illumination Si/Ge uni-traveling carrier (UTC) devices suffer from inter-constraint between high speed and high responsivity. Here, we report a high responsivity vertical-illumination Si/Ge UTC photodiode based on a silicon-on-insulator substrate. When the transmission of the monolayer anti-reflection coating was maximum, the maximum absorption efficiency of the devices was 1.45 times greater than the silicon substrate owing to constructive interference. The Si/Ge UTC photodiode had a dominant responsivity at 1550 nm of 0.18 A/W, a 50% improvement even with a 25% thinner Ge absorption layer.

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.…”

Simulation of optical properties of semiconductor multilayers from extreme ultraviolet to far infrared

“…In this study, the radiative properties of SOI structures, based on the earlier studies of Ravindra et al 11 on SIMOX (Separation by IMplanted Oxygen) structures, with 200-nm Si/400-nm SiO 2 /Sisubstrate, as the control group, are considered to demonstrate the validity of the proposed simulation model. In Figure 1A, A case study, based on Li et al 12 considering the thickness of Si as 1000 nm on top of a 2000 nm thick SiO 2 , is presented. Another case study is based on Badri et al 13 with the thickness of SiO 2 as 2000 nm with the top layer of Si varying in thickness from 75 to 325nm.…”

“…The thickness of Ge layer is varied from 400 to1200 nm in steps of 200nm (i.e., 400, 600, 800, 1000, 1200 nm) and the thickness of bulk Si or SOI substrates consisting of thin SiO 2 and silicon layer (150nm Si on 400nm SiO 2 decreasing to 60nm Si on 150nm SiO 2 ) 14 are considered. ' ' ( ) ( ) Besides, another interesting case study, based on Chong et al 12 on coupled waveguides of Ge-on-SOI (Si/Ge/Si/Si/SiO 2 /Si), as shown in Figure 1d, with the thickness of Si (100nm), Ge (1000nm), Si(600 nm), Si(220nm) and SiO 2 (2000nm), respectively, is investigated. Besides the Ge photodetector, we also report the optical properties of Ge x Si 1-x (x = 0.05, 0.1 and 0.15) alloys on Si by varying the thickness of Ge x Si 1-x from 100-1000 nm based on the case study of Kadri et al 15 The simulations are implemented in MATLAB using fitting parameters based on Forouhi-Bloomer dispersion model for the n and k of Si, Ge, SiGe and SiO 2 , as shown in Table 1.…”

Plasmonic Photodetectors

“…The existence of a depletion region -created by application of a reverse bias to the junction -results in a low dark current value [37]. Still, this structure is not optimal from the point of view of carrier extraction speed since a bulk charge appearing due the difference in mobility of electrons and holes limits the detector bandwidth [38], [39]. The latter is addressed by UTC (Uni-Traveling-Carrier) photodiodes that use heterostructures to make only electrons contribute to the signal current [38]- [41].…”