**3. Schottky silicon photodetectors based on 2D materials**

In last years, graphene has revolutionized the world of photonics and electronics thanks to its exceptional properties. Since its discovery, many researchers have concentrated their efforts on the possibility to integrate the graphene into optoelectronic devices. Notably, its zero direct bandgap make it very attractive for photodetection on a wide range from UV to IR. In particular, the demonstration of the graphene/silicon Schottky junction [39] has opened the path to realize more efficient NIR photodetectors exploiting the IPE.

with a peak value of the responsivity at 1.55 μm of 20mAW�<sup>1</sup>

*DOI: http://dx.doi.org/10.5772/intechopen.99625*

*Near-Infrared Schottky Silicon Photodetectors Based on Two Dimensional Materials*

theoretically discussed [43].

enhance the graphene absorption.

**Figure 5.**

**101**

voltage. At such bias the dark current was 147 μA. The authors also evaluated the NEP and the bandwidth of the devices, that resulted 3.5 x 10�<sup>10</sup> WHz�<sup>1</sup> and 120 MHz, respectively. Furthermore, it is worth noting that the Fabry-Perot cavity with a finesse of 5.4 determined a high spectral selectivity that could be easily tuned by changing the length of the resonant structure. The same author has devised another device, theoretically investigated in [41, 42], where the SLG was situated in the centre of c-Si/a-Si:H optical cavity. The photodetection mechanism is based on IPE through the SLG/c-Si junction. The resonant structure, embedded between two high reflectivity dielectric mirrors, enabled an increased number of round-trips of the radiation that crossed multiple times the graphene layer strongly increasing its absorption. This not only provides a 100% maximum SLG absorption but also a responsivity and a finesse of 0.43 A/W and 172 in a correctly designed PD. Further, in this work the bandwidth and the noise of the device were discussed. In addition, a similar device taking advantage of a double silicon on insulator substrate working as a high-reflectivity mirror has been recently proposed and

In 2016 Chen et al. [44] demonstrated graphene short-wave SWIR PDs with a very high responsivity of 83A/W at 1.55 μm thanks to the combination of two different mechanisms that allow the improvement of the performances of their devices. Indeed, they overcome the problems of the low optical absorption and the short lifetime of the photogenerated charge carriers by exploiting plasmonic effects and a vertical built-in field at the graphene/silicon interface. The exploitation of the plasmonic effects occurs through a gold nanoparticles (Au NPs) array on the graphene channel (**Figure 5a**). By tuning their shape and size, the gold NPs traps and absorbs the light at the resonance wavelength, resulting in a very high absorption that allows a greater photogeneration of charge carriers in the graphene (**Figure 5b**). Then, the vertical built-in potential at the interface between the graphene and the silicon induces a sort of carrier-trapping effect, by guiding the electrons away of the graphene and thus by generating holes with a consequent longer carrier lifetime. Indeed, the extension of the built- in field along all the large heterojunction produces a diminishing of the carrier recombination. This work shows how the Schottky junctions can play a relevant role in the field of SP in the context of NIR detection and demonstrates the need to exploit new structures to

Recently, it has been proved that graphene/Si PDs based on the IPE can operate also at wavelengths greater than 1.55um. In [40] Casalino et al. reported the first

*a) Schematic illustration of the graphene SWIR PD reported in [44]. In b) the comparison between the photoresponse of the devices with and without gold nanoparticles at vary illumination powers. Reprinted with*

*permission from ACS Nano 2017, 11, 1, 430–437. Copyright 2017 American Chemical Society.*

at -10 V applied

In 2013, Amirmazlaghani et al. investigated a NIR PD based on exfoliated graphite on the top of a silicon substrate [34]. The Schottky barrier at the interface between the two materials resulted 0.44–0.47 eV and the ideality factor was 1.3–2.1. When a reverse bias of 16 V was applied, the device exhibited a dark current of the order of μA and, under a 1.55 μm illumination, a maximum responsivity of 9.9 mAW�<sup>1</sup> . This value, higher than the one predicted by the Eq. (4), was explained by the authors as a consequence of the of the linear dispersion in graphene that requires a correction of the modified Fowler theory. By taking into account the twodimensional nature of the graphene they derived the Eq. (5) able to provide a better agreement with the experimental data. This issue was confirmed by Goykhman et al. who in 2016 demonstrated an increase in efficiency of 7% with respect to the values predicted by the Eq. (4). The device investigated in [4] is a 5 μm silicon waveguide covered by a layer of graphene. The plasmonic enhancement was obtained thanks to a film of Au on the top of the graphene. At 1 V reverse bias the authors reported a responsivity of 85mAW�<sup>1</sup> , that could grow up to 0.37AW�<sup>1</sup> at a reverse voltage of -3 V. This happens thanks to an avalanche multiplication effect that unfortunately caused an abrupt increment of the dark current from 20 nA to 3 μA. Recently, Levy et al. [36] have proposed a phenomenological theory to explain the enhancement of internal photoemission in gold/graphene/silicon plasmonic structures.

In 2017 Casalino et al. realized vertically illuminated resonant cavity enhanced PDs exploiting the IPE through a CVD grown Single Layer Graphene (SLG) placed on top of a silicon substrate provided of a gold mirror on the back which acted as an optical cavity (**Figure 4a**) [40]. This optical microcavity allowed to trap the radiation increasing the light round-trips in the cavity and enhancing the SLG optical absorption. A wavelength-dependent photoresponse was achieved (**Figure 4b**)

#### **Figure 4.**

*Sketch (a) and PDs spectral photoresponse (b) of the resonant cavity enhanced PDs investigated by Casalino et al. [40]. Reprinted with permission from ACS Nano 2017, 11, 11, 10955–10963. Copyright 2017 American Chemical Society.*

#### *Near-Infrared Schottky Silicon Photodetectors Based on Two Dimensional Materials DOI: http://dx.doi.org/10.5772/intechopen.99625*

with a peak value of the responsivity at 1.55 μm of 20mAW�<sup>1</sup> at -10 V applied voltage. At such bias the dark current was 147 μA. The authors also evaluated the NEP and the bandwidth of the devices, that resulted 3.5 x 10�<sup>10</sup> WHz�<sup>1</sup> and 120 MHz, respectively. Furthermore, it is worth noting that the Fabry-Perot cavity with a finesse of 5.4 determined a high spectral selectivity that could be easily tuned by changing the length of the resonant structure. The same author has devised another device, theoretically investigated in [41, 42], where the SLG was situated in the centre of c-Si/a-Si:H optical cavity. The photodetection mechanism is based on IPE through the SLG/c-Si junction. The resonant structure, embedded between two high reflectivity dielectric mirrors, enabled an increased number of round-trips of the radiation that crossed multiple times the graphene layer strongly increasing its absorption. This not only provides a 100% maximum SLG absorption but also a responsivity and a finesse of 0.43 A/W and 172 in a correctly designed PD. Further, in this work the bandwidth and the noise of the device were discussed. In addition, a similar device taking advantage of a double silicon on insulator substrate working as a high-reflectivity mirror has been recently proposed and theoretically discussed [43].

In 2016 Chen et al. [44] demonstrated graphene short-wave SWIR PDs with a very high responsivity of 83A/W at 1.55 μm thanks to the combination of two different mechanisms that allow the improvement of the performances of their devices. Indeed, they overcome the problems of the low optical absorption and the short lifetime of the photogenerated charge carriers by exploiting plasmonic effects and a vertical built-in field at the graphene/silicon interface. The exploitation of the plasmonic effects occurs through a gold nanoparticles (Au NPs) array on the graphene channel (**Figure 5a**). By tuning their shape and size, the gold NPs traps and absorbs the light at the resonance wavelength, resulting in a very high absorption that allows a greater photogeneration of charge carriers in the graphene (**Figure 5b**). Then, the vertical built-in potential at the interface between the graphene and the silicon induces a sort of carrier-trapping effect, by guiding the electrons away of the graphene and thus by generating holes with a consequent longer carrier lifetime. Indeed, the extension of the built- in field along all the large heterojunction produces a diminishing of the carrier recombination. This work shows how the Schottky junctions can play a relevant role in the field of SP in the context of NIR detection and demonstrates the need to exploit new structures to enhance the graphene absorption.

Recently, it has been proved that graphene/Si PDs based on the IPE can operate also at wavelengths greater than 1.55um. In [40] Casalino et al. reported the first

#### **Figure 5.**

**3. Schottky silicon photodetectors based on 2D materials**

*Light-Emitting Diodes and Photodetectors - Advances and Future Directions*

efficient NIR photodetectors exploiting the IPE.

authors reported a responsivity of 85mAW�<sup>1</sup>

mAW�<sup>1</sup>

structures.

**Figure 4.**

**100**

*American Chemical Society.*

In last years, graphene has revolutionized the world of photonics and electronics

thanks to its exceptional properties. Since its discovery, many researchers have concentrated their efforts on the possibility to integrate the graphene into optoelectronic devices. Notably, its zero direct bandgap make it very attractive for photodetection on a wide range from UV to IR. In particular, the demonstration of the graphene/silicon Schottky junction [39] has opened the path to realize more

In 2013, Amirmazlaghani et al. investigated a NIR PD based on exfoliated graphite on the top of a silicon substrate [34]. The Schottky barrier at the interface between the two materials resulted 0.44–0.47 eV and the ideality factor was 1.3–2.1. When a reverse bias of 16 V was applied, the device exhibited a dark current of the order of μA and, under a 1.55 μm illumination, a maximum responsivity of 9.9

the authors as a consequence of the of the linear dispersion in graphene that requires a correction of the modified Fowler theory. By taking into account the twodimensional nature of the graphene they derived the Eq. (5) able to provide a better agreement with the experimental data. This issue was confirmed by Goykhman et al. who in 2016 demonstrated an increase in efficiency of 7% with respect to the values predicted by the Eq. (4). The device investigated in [4] is a 5 μm silicon waveguide covered by a layer of graphene. The plasmonic enhancement was obtained thanks to a film of Au on the top of the graphene. At 1 V reverse bias the

reverse voltage of -3 V. This happens thanks to an avalanche multiplication effect that unfortunately caused an abrupt increment of the dark current from 20 nA to 3 μA. Recently, Levy et al. [36] have proposed a phenomenological theory to explain the enhancement of internal photoemission in gold/graphene/silicon plasmonic

In 2017 Casalino et al. realized vertically illuminated resonant cavity enhanced PDs exploiting the IPE through a CVD grown Single Layer Graphene (SLG) placed on top of a silicon substrate provided of a gold mirror on the back which acted as an optical cavity (**Figure 4a**) [40]. This optical microcavity allowed to trap the radiation increasing the light round-trips in the cavity and enhancing the SLG optical absorption. A wavelength-dependent photoresponse was achieved (**Figure 4b**)

*Sketch (a) and PDs spectral photoresponse (b) of the resonant cavity enhanced PDs investigated by Casalino et al. [40]. Reprinted with permission from ACS Nano 2017, 11, 11, 10955–10963. Copyright 2017*

. This value, higher than the one predicted by the Eq. (4), was explained by

, that could grow up to 0.37AW�<sup>1</sup> at a

*a) Schematic illustration of the graphene SWIR PD reported in [44]. In b) the comparison between the photoresponse of the devices with and without gold nanoparticles at vary illumination powers. Reprinted with permission from ACS Nano 2017, 11, 1, 430–437. Copyright 2017 American Chemical Society.*

demonstration of free-space vertically-illuminated PDs operating under a 2 μm radiation. Through an electrical analysis in a range of temperature from 280 to 315°C, they extracted the value of the SBH resulted to be 0.62 eV at 300 K. From the analysis it emerged a temperature dependence of the SBH which has been ascribed to the presence of defect at the interface between graphene and silicon. The proposed devices show at zero bias an internal responsivity of 10.3 mA/W, corresponding to an external one of 0.16 mA/W, accordingly to the theorical predictions.

an open-circuit voltage of 210 mV together with a remarkable signal-to-noise ratio

*Near-Infrared Schottky Silicon Photodetectors Based on Two Dimensional Materials*

As shown in **Figure 6b**, the photoresponse of the device spanned the range of wavelengths from UV to NIR with peak responsivity values of 5-6mAW<sup>1</sup> at 420, 680, 800 and 1000 nm suggesting a an excitonic absorption of the WS2. In addition, Kim et al. analyzed the transient photocurrent at various wavelengths allowing to evaluate the photoresponse speed of the photodetectors that results to be about 1.1 μs for a 10 kHz modulated signal, very higher than the conventional Si UV photodetectors. This impressive performance can be attributed to the large in-plane

Very interestingly, in 2019 Ahmad et al. reported a photodetector based on a WS2 monolayer/Si junction [30]. The WS2 monolayer was characterized by a lower bandgap with respect to the bulk material enabling higher responsivity of 10.46 mAW<sup>1</sup> at 785 nm. On the other hand, such configuration did not permit to take advantage of the in-plane conductivity of the absorber medium, resulting in a

Another emerging 2D TMDC is the platinum diselenide (PtSe2). Its bandgap, ranging from zero in the monolayer to 1.2 eV in the bulk, make it very promising for the NIR photodetection. Recently, Xie et al. investigated PDs exploiting a multilayered PtSe2/silicon heterojunction [31]. In their work a thermally assisted conversion was used in order to have the *in situ* preparation of the PtSe2 on the silicon substrate. Such technique permitted to realize interfaces with a small number of defects that

, respectively. Such

greater than 9000 for an incident radiation of 850 nm.

*DOI: http://dx.doi.org/10.5772/intechopen.99625*

slower response of 186.7 ms for a 20 kHz modulated signal.

and 1550 nm with a responsivity of 33.25 and 0.57mAW<sup>1</sup>

TMDC PDs based on vertical structure.

**4. Conclusions**

**103**

would trap the photogenerated carriers. The XRD patterns displayed a policrystalline structure with nanometer-sized crystalline domains. The asdeposited 14.5 nm-thick film, corresponding to about 17 layers of PtS2, can be accordingly considered as a semimetal. The I-V curves confirmed the rectifying nature of the heterojunction in the range within 5 V and the ideality factor was estimated to be about 1.64. The PDs could operate in a wide spectrum ranging from 200 to 1550 nm with a maximum responsivity of 520mAW<sup>1</sup> at 808 nm. This device showed also the capability to detect the telecommunication wavelengths of 1310

results were attributed to the high NIR radiation optical absorption of the PtSe2 layer. It is worth mentioning that these PDs showed a fast response, indeed, the rise time and fall time were 55.3 and 170.5 μs, respectively. The clean interfaces obtained thanks to the *in situ* preparation strongly influenced the performance of the device that exhibited a response speed comparable to the above mentioned works on

In this chapter the physical principles of NIR Schottky PDs based on 2D materials have been elucidated and the main devices reported in literature have been discussed. In particular, PDs exploiting the IPE among 2D layered materials and silicon are deepened since to date they represent the most promising approach for the realization of high performances Si-based PDs. Devices discussed along this chapter have been summarized in **Table 1** to allow an immediate comparison of their performance. It emerges that the low absorption coefficient of the graphene makes indispensable the use of structures enabling the light trapping for enhancing the light-matter interaction. Indeed, devices exploiting resonant cavities, waveguides and plasmonic effects result to have best performances in terms of responsivity. These structures show performance comparable with the wellestablished germanium technology adding the potentialities to detect wavelength

charge WS2 carrier mobility.

In last years, there has been increasing interest in others 2D layered materials. In particular, TMDCs have emerged thanks to the attractive possibility to tune their bandgaps through the quantity of layers as well as their exceptional electronic and optical properties.

Molybdenum disulfide (MoS2) is characterized by an indirect bandgap of about 1.3 eV that increases up to 1.8 eV and changes into a direct one in the monolayer.

In 2015, Wang et al. presented a MoS2/Si heterojunction based on vertically standing layered configuration for the realization of ultrafast photodetectors [28]. The deposition of MoS2 via sputtering allowed the growth of a policrystalline film with a vertical structure, from the p-silicon substrate up to the Ag electrode, enabling the exploitation of the high in-plane mobility of the MoS2. The electrical analysis of the junctions showed a potential barrier at the interface between the two materials of 0.33 eV while the good quality of the junction was proved by an ideality factor of 1.83 and a rectification ratio of about 5000. The PD worked over a broadband spectrum, from visible to near infrared, with a maximum responsivity of 300mAW<sup>1</sup> at 808 nm. The low dark current of the junction ensured a high detectivity up to 1013Jones and a fast response of 2 μs. Furthermore, the PD exhibited a photovoltaic behavior by producing a photovoltage and a photocurrent of 210 mV and 100 μA, respectively, at open circuit and zero bias.

Subsequently, Kim et al. have proposed a similar PD based on a tungsten disulphite active layer [29]. Thanks to a bottom-up approach, by using a magnetron sputtering, they were able to grow vertical WS2 layers onto a p-Si wafer at different temperatures **Figure 6a**. Through the X-Rays Diffraction (XRD) analysis they found a highly crystalline structure in the layers deposited at 400°C.

The I-V curves demonstrated the formation of the heterojunction and the rectifying behavior within 2 V where the rectification ratio was about 20000. The ideality factor and the dark saturation current IS were estimated to be 1.43 and 0.1 μA, respectively. The WS2/Si junction exhibited a zero-bias photoresponse and

#### **Figure 6.**

*a) Sketch and photograph of the WS2/p-Si based PD investigated by [29] et al. and b) spectral photoresponse of the device. Reprinted with permission from ACS Appl. Mater. Interfaces 2018, 10, 4, 3964–3974. Copyright 2018 American Chemical Society.*

#### *Near-Infrared Schottky Silicon Photodetectors Based on Two Dimensional Materials DOI: http://dx.doi.org/10.5772/intechopen.99625*

an open-circuit voltage of 210 mV together with a remarkable signal-to-noise ratio greater than 9000 for an incident radiation of 850 nm.

As shown in **Figure 6b**, the photoresponse of the device spanned the range of wavelengths from UV to NIR with peak responsivity values of 5-6mAW<sup>1</sup> at 420, 680, 800 and 1000 nm suggesting a an excitonic absorption of the WS2. In addition, Kim et al. analyzed the transient photocurrent at various wavelengths allowing to evaluate the photoresponse speed of the photodetectors that results to be about 1.1 μs for a 10 kHz modulated signal, very higher than the conventional Si UV photodetectors. This impressive performance can be attributed to the large in-plane charge WS2 carrier mobility.

Very interestingly, in 2019 Ahmad et al. reported a photodetector based on a WS2 monolayer/Si junction [30]. The WS2 monolayer was characterized by a lower bandgap with respect to the bulk material enabling higher responsivity of 10.46 mAW<sup>1</sup> at 785 nm. On the other hand, such configuration did not permit to take advantage of the in-plane conductivity of the absorber medium, resulting in a slower response of 186.7 ms for a 20 kHz modulated signal.

Another emerging 2D TMDC is the platinum diselenide (PtSe2). Its bandgap, ranging from zero in the monolayer to 1.2 eV in the bulk, make it very promising for the NIR photodetection. Recently, Xie et al. investigated PDs exploiting a multilayered PtSe2/silicon heterojunction [31]. In their work a thermally assisted conversion was used in order to have the *in situ* preparation of the PtSe2 on the silicon substrate. Such technique permitted to realize interfaces with a small number of defects that would trap the photogenerated carriers. The XRD patterns displayed a policrystalline structure with nanometer-sized crystalline domains. The asdeposited 14.5 nm-thick film, corresponding to about 17 layers of PtS2, can be accordingly considered as a semimetal. The I-V curves confirmed the rectifying nature of the heterojunction in the range within 5 V and the ideality factor was estimated to be about 1.64. The PDs could operate in a wide spectrum ranging from 200 to 1550 nm with a maximum responsivity of 520mAW<sup>1</sup> at 808 nm. This device showed also the capability to detect the telecommunication wavelengths of 1310 and 1550 nm with a responsivity of 33.25 and 0.57mAW<sup>1</sup> , respectively. Such results were attributed to the high NIR radiation optical absorption of the PtSe2 layer. It is worth mentioning that these PDs showed a fast response, indeed, the rise time and fall time were 55.3 and 170.5 μs, respectively. The clean interfaces obtained thanks to the *in situ* preparation strongly influenced the performance of the device that exhibited a response speed comparable to the above mentioned works on TMDC PDs based on vertical structure.

### **4. Conclusions**

demonstration of free-space vertically-illuminated PDs operating under a 2 μm radiation. Through an electrical analysis in a range of temperature from 280 to 315°C, they extracted the value of the SBH resulted to be 0.62 eV at 300 K. From the analysis it emerged a temperature dependence of the SBH which has been ascribed to the presence of defect at the interface between graphene and silicon. The proposed devices show at zero bias an internal responsivity of 10.3 mA/W, corresponding to an external one of 0.16 mA/W, accordingly to the theorical

*Light-Emitting Diodes and Photodetectors - Advances and Future Directions*

In last years, there has been increasing interest in others 2D layered materials. In particular, TMDCs have emerged thanks to the attractive possibility to tune their bandgaps through the quantity of layers as well as their exceptional electronic and

Molybdenum disulfide (MoS2) is characterized by an indirect bandgap of about 1.3 eV that increases up to 1.8 eV and changes into a direct one in the monolayer. In 2015, Wang et al. presented a MoS2/Si heterojunction based on vertically standing layered configuration for the realization of ultrafast photodetectors [28]. The deposition of MoS2 via sputtering allowed the growth of a policrystalline film with a vertical structure, from the p-silicon substrate up to the Ag electrode, enabling the exploitation of the high in-plane mobility of the MoS2. The electrical analysis of the junctions showed a potential barrier at the interface between the two materials of 0.33 eV while the good quality of the junction was proved by an ideality

factor of 1.83 and a rectification ratio of about 5000. The PD worked over a

of 210 mV and 100 μA, respectively, at open circuit and zero bias.

found a highly crystalline structure in the layers deposited at 400°C.

broadband spectrum, from visible to near infrared, with a maximum responsivity of 300mAW<sup>1</sup> at 808 nm. The low dark current of the junction ensured a high detectivity up to 1013Jones and a fast response of 2 μs. Furthermore, the PD

exhibited a photovoltaic behavior by producing a photovoltage and a photocurrent

The I-V curves demonstrated the formation of the heterojunction and the recti-

*a) Sketch and photograph of the WS2/p-Si based PD investigated by [29] et al. and b) spectral photoresponse of the device. Reprinted with permission from ACS Appl. Mater. Interfaces 2018, 10, 4, 3964–3974. Copyright*

Subsequently, Kim et al. have proposed a similar PD based on a tungsten disulphite active layer [29]. Thanks to a bottom-up approach, by using a magnetron sputtering, they were able to grow vertical WS2 layers onto a p-Si wafer at different temperatures **Figure 6a**. Through the X-Rays Diffraction (XRD) analysis they

fying behavior within 2 V where the rectification ratio was about 20000. The ideality factor and the dark saturation current IS were estimated to be 1.43 and 0.1 μA, respectively. The WS2/Si junction exhibited a zero-bias photoresponse and

predictions.

**Figure 6.**

**102**

*2018 American Chemical Society.*

optical properties.

In this chapter the physical principles of NIR Schottky PDs based on 2D materials have been elucidated and the main devices reported in literature have been discussed. In particular, PDs exploiting the IPE among 2D layered materials and silicon are deepened since to date they represent the most promising approach for the realization of high performances Si-based PDs. Devices discussed along this chapter have been summarized in **Table 1** to allow an immediate comparison of their performance. It emerges that the low absorption coefficient of the graphene makes indispensable the use of structures enabling the light trapping for enhancing the light-matter interaction. Indeed, devices exploiting resonant cavities, waveguides and plasmonic effects result to have best performances in terms of responsivity. These structures show performance comparable with the wellestablished germanium technology adding the potentialities to detect wavelength


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[1] Yole Dèvelop. [Internet]. 2020 Available from: http://www.yole.fr/Si\_ Photonics\_Datacom\_Sensing.aspx

*DOI: http://dx.doi.org/10.5772/intechopen.99625*

Symposium East, Arlington, VA, USA,

[10] Kosonocky, W.F., Elabd, H., Erhardt, H.G., Shallcross, F.V., Villani, T., Meray, G., Cantella, M.J., Klein, J., Roberts, N. 64 ⇥ 128-Elements High-Performance PtSi IR-CCD Image Sensor. In Proceedings of the 1981 International Electron Devices Meeting, Washington, DC, USA, 7–9 December

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[12] Wang, W. L., Winzenread, R., Nguyen, B., Murrin, J.J. High fill factor 512 x 512 PtSi focal plane array. In: Proceedings of the SPIE's 33rd Annual Technical Symposium, San Diego, CA,

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[14] Casalino, M.; Sirleto, L.; Moretti, L.; Della Corte, F.; Rendina, I.: Design of a silicon resonant cavity enhanced photodetector based on the internal photoemission effect at 1.55 μm. Journal of Optics A: Pure and applied optics,

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*Near-Infrared Schottky Silicon Photodetectors Based on Two Dimensional Materials*

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[5] Alavirad, M., Roy, L., & Berini, P.:

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[9] Elabd, H.; Villani, T.S.; Tower, J.R.: High density Schottky-barrier IRCCD sensors for SWIR applications at intermediated temperature. In Proceedings of the SPIE's Technical

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#### **Table 1.**

*Comparison of the main electrical and optical parameters of the 2D materials/Si NIR PDs reported in this chapter.*

longer than 1550 nm. Although most of the Schottky PDs are based on graphene, more recently others 2D materials have stood out showing promising outcomes in the NIR spectrum.

Thanks to the easy fabrication processes and the low cost of production, this new family of PDs represents a breakthrough, opening the way towards the commercial integration of silicon in photonics.
