Title: Intrinsic Photoconductivity of few-layered ZrS2 Phototransistors via Multiterminal Measurements
We report intrinsic photoconductivity studies on one of the least examined layered compounds, ZrS2.Few-atomic layer ZrS2 field-effect transistors were fabricated on the Si/SiO2 substrate and photoconductivity measurements were performed using both two- and four-terminal configurations under the illumination of 532 nm laser source. We measured photocurrent as a function of the incident optical power at several source-drain (bias) voltages. We observe a significantly large photoconductivity when measured in the multiterminal (four-terminal) configuration compared to that in the two-terminal configuration. For an incident optical power of 90 nW, the estimated photosensitivity and the external quantum efficiency (EQE) measured in two-terminal configuration are 0.5 A/W and 120%, respectively, under a bias voltage of 650 mV. Under the same conditions, the four-terminal measurements result in much higher values for both the photoresponsivity (R) and EQE to 6 A/W and 1400%, respectively. This significant improvement in photoresponsivity and EQE in the four-terminal configuration may have been influenced by the reduction of contact resistance at the metal-semiconductor interface, which greatly impacts the carrier mobility of low conducting materials. This suggests that photoconductivity measurements performed through the two-terminal configuration in previous studies on ZrS2 and other 2D materials have severely underestimated the true intrinsic properties of transition metal dichalcogenides and their remarkable potential for optoelectronic applications. more »« less
Das, Priyanka; Nash, Jawnaye; Webb, Micah; Burns, Raelyn; Mapara, Varun N.; Ghimire, Govinda; Rosenmann, Daniel; Divan, Ralu; Karaiskaj, Denis; McGill, Stephen A.; et al
(, Nanoscale)
null
(Ed.)
Among the layered two dimensional semiconductors, molybdenum disulfide (MoS 2 ) is considered to be an excellent candidate for applications in optoelectronics and integrated circuits due to its layer-dependent tunable bandgap in the visible region, high ON/OFF current ratio in field-effect transistors (FET) and strong light–matter interaction properties. In this study, using multi-terminal measurements, we report high broadband photocurrent response ( R ) and external quantum efficiency (EQE) of few-atomic layered MoS 2 phototransistors fabricated on a SiO 2 dielectric substrate and encapsulated with a thin transparent polymer film of Cytop. The photocurrent response was measured using a white light source as well as a monochromatic light of wavelength λ = 400 nm–900 nm. We measured responsivity using a 2-terminal configuration as high as R = 1 × 10 3 A W −1 under white light illumination with an optical power P opt = 0.02 nW. The R value increased to 3.5 × 10 3 A W −1 when measured using a 4-terminal configuration. Using monochromatic light on the same device, the measured values of R were 10 3 and 6 × 10 3 A W −1 under illumination of λ = 400 nm when measured using 2- and 4-terminal methods, respectively. The highest EQE values obtained using λ = 400 nm were 10 5 % and 10 6 % measured using 2- and 4-terminal configurations, respectively. The wavelength dependent responsivity decreased from 400 nm to the near-IR region at 900 nm. The observed photoresponse, photocurrent–dark current ratio (PDCR), detectivity as a function of applied gate voltage, optical power, contact resistances and wavelength were measured and are discussed in detail. The observed responsivity is also thoroughly studied as a function of contact resistance of the device.
Patil, Prasanna Dnyaneshwar; Wasala, Milinda; Alkhaldi, Rana; Weber, Lincoln; Kovi, Kiran Kumar; Chakrabarti, Bhaswar; Nash, Jawnaye; Rhodes, Daniel; Rosenmann, Daniel; Divan, Ralu; et al
(, Journal of Materials Chemistry C)
null
(Ed.)
A wide variety of two-dimensional (2D) metal dichalcogenide compounds have recently attracted much research interest due to their very high photoresponsivities (R) making them excellent candidates for optoelectronic applications. High R in 2D photoconductors is associated to trap state dynamics leading to a photogating effect, which is often manifested by a fractional power dependence (γ) of the photocurrent (I ph ) when under an effective illumination intensity (P eff ). Here we present photoconductivity studies as a function of gate voltages, over a wide temperature range (20 K to 300 K) of field-effect transistors fabricated using thin layers of mechanically exfoliated rhenium diselenide (ReSe 2 ). We obtain very high responsivities R ~ 16500 A/W and external quantum efficiency (EQE) ~ 3.2 x 10 6 % (at 140 K, V g = 60 V and P eff = 0.2 nW). A strong correlation between R and γ was established by investigating the dependence of these two quantities at various gate voltages and over a wide range of temperature. Such correlations indicate the importance of trap state mediated photogating and its role in promoting high photo responsivities in these materials. We believe such correlations can offer valuable insights for the design and development of high performance photoactive devices using 2D materials.
Golani, Prafful; Saha, Chinmoy Nath; Sundaram, Prakash P.; Liu, Fengdeng; Truttmann, Tristan K.; Chaganti, V. R. Saran Kumar; Jalan, Bharat; Singisetti, Uttam; Koester, Steven J.
(, Applied Physics Letters)
This work reports the quantification of rise in channel temperature due to self-heating in two-terminal SrSnO3 thin film devices under electrical bias. Using pulsed current–voltage (I–V) measurements, thermal resistances of the thin films were determined by extracting the relationship between the channel temperature and the dissipated power. For a 26-nm-thick n-doped SrSnO3 channel with an area of 200 μm2, a thermal resistance of 260.1 ± 24.5 K mm/W was obtained. For a modest dissipated power of 0.5 W/mm, the channel temperature rose to ∼176 °C, a value which increases further at higher power levels. Electro-thermal simulations were performed which showed close agreement between the simulated and experimental I–V characteristics both in the absence and presence of self-heating. The work presented is critical for the development of perovskite-based high-power electronic devices.
Jayanand, Kishan; Chugh, Srishti; Adhikari, Nirmal; Min, Misook; Echegoyen, Luis; Kaul, Anupama B.
(, Journal of Materials Chemistry C)
High-performance hybrid graphene photodetectors were prepared with endohedral fullerenes deposited on graphene using electrophoretic methods for the first time. Endohedral Sc 3 N@C 80 , which acts as an electron acceptor, was used and the ensuing electronic and optoelectronic properties were measured. Another endohedral fullerene, La@C 82 , was also adsorbed on graphene, which acts as an electron donor. Upon optical illumination, for the Sc 3 N@C 80 –graphene hybrid, the photoinduced free holes are injected into graphene, increasing the hole carrier concentration in graphene, while the photoexcited electrons remain in Sc 3 N@C 80 ; this leads to a high photoresponsivity of ∼10 9 A W −1 , detectivity D of ∼10 15 Jones, and external quantum efficiency EQE ∼ 10 9 % for the Sc 3 N@C 80 –graphene hybrid. This is ∼10 times higher compared to other reports of quantum dot-graphene and few layer MoS 2 –graphene heterostructures. Similarly, for the La@C 82 –graphene hybrid, ∼ 10 8 A W −1 , D ∼ 10 14 Jones, and EQE ∼ 10 6 % were achieved, with electrons being injected into graphene. The exceptional performance gains achieved with both types of hybrid structures confirms the potential of endohedrals to dope graphene for high performance optoelectronic devices using a facile and scalable fabrication process.
BACKGROUND Optical sensing devices measure the rich physical properties of an incident light beam, such as its power, polarization state, spectrum, and intensity distribution. Most conventional sensors, such as power meters, polarimeters, spectrometers, and cameras, are monofunctional and bulky. For example, classical Fourier-transform infrared spectrometers and polarimeters, which characterize the optical spectrum in the infrared and the polarization state of light, respectively, can occupy a considerable portion of an optical table. Over the past decade, the development of integrated sensing solutions by using miniaturized devices together with advanced machine-learning algorithms has accelerated rapidly, and optical sensing research has evolved into a highly interdisciplinary field that encompasses devices and materials engineering, condensed matter physics, and machine learning. To this end, future optical sensing technologies will benefit from innovations in device architecture, discoveries of new quantum materials, demonstrations of previously uncharacterized optical and optoelectronic phenomena, and rapid advances in the development of tailored machine-learning algorithms. ADVANCES Recently, a number of sensing and imaging demonstrations have emerged that differ substantially from conventional sensing schemes in the way that optical information is detected. A typical example is computational spectroscopy. In this new paradigm, a compact spectrometer first collectively captures the comprehensive spectral information of an incident light beam using multiple elements or a single element under different operational states and generates a high-dimensional photoresponse vector. An advanced algorithm then interprets the vector to achieve reconstruction of the spectrum. This scheme shifts the physical complexity of conventional grating- or interference-based spectrometers to computation. Moreover, many of the recent developments go well beyond optical spectroscopy, and we discuss them within a common framework, dubbed “geometric deep optical sensing.” The term “geometric” is intended to emphasize that in this sensing scheme, the physical properties of an unknown light beam and the corresponding photoresponses can be regarded as points in two respective high-dimensional vector spaces and that the sensing process can be considered to be a mapping from one vector space to the other. The mapping can be linear, nonlinear, or highly entangled; for the latter two cases, deep artificial neural networks represent a natural choice for the encoding and/or decoding processes, from which the term “deep” is derived. In addition to this classical geometric view, the quantum geometry of Bloch electrons in Hilbert space, such as Berry curvature and quantum metrics, is essential for the determination of the polarization-dependent photoresponses in some optical sensors. In this Review, we first present a general perspective of this sensing scheme from the viewpoint of information theory, in which the photoresponse measurement and the extraction of light properties are deemed as information-encoding and -decoding processes, respectively. We then discuss demonstrations in which a reconfigurable sensor (or an array thereof), enabled by device reconfigurability and the implementation of neural networks, can detect the power, polarization state, wavelength, and spatial features of an incident light beam. OUTLOOK As increasingly more computing resources become available, optical sensing is becoming more computational, with device reconfigurability playing a key role. On the one hand, advanced algorithms, including deep neural networks, will enable effective decoding of high-dimensional photoresponse vectors, which reduces the physical complexity of sensors. Therefore, it will be important to integrate memory cells near or within sensors to enable efficient processing and interpretation of a large amount of photoresponse data. On the other hand, analog computation based on neural networks can be performed with an array of reconfigurable devices, which enables direct multiplexing of sensing and computing functions. We anticipate that these two directions will become the engineering frontier of future deep sensing research. On the scientific frontier, exploring quantum geometric and topological properties of new quantum materials in both linear and nonlinear light-matter interactions will enrich the information-encoding pathways for deep optical sensing. In addition, deep sensing schemes will continue to benefit from the latest developments in machine learning. Future highly compact, multifunctional, reconfigurable, and intelligent sensors and imagers will find applications in medical imaging, environmental monitoring, infrared astronomy, and many other areas of our daily lives, especially in the mobile domain and the internet of things. Schematic of deep optical sensing. The n -dimensional unknown information ( w ) is encoded into an m -dimensional photoresponse vector ( x ) by a reconfigurable sensor (or an array thereof), from which w′ is reconstructed by a trained neural network ( n ′ = n and w′ ≈ w ). Alternatively, x may be directly deciphered to capture certain properties of w . Here, w , x , and w′ can be regarded as points in their respective high-dimensional vector spaces ℛ n , ℛ m , and ℛ n ′ .
Tanthirige, Rukshan M., Garcia, Carlos, Ghosh, Saikat, II, Frederick Jackson, Nash, Jawnaye, Rosenmann, Daniel, Divan, Ralu, Stan, Liliana, Sumant, Anirudha V., McGill, Stephen A., Ray, Paresh C., and Pradhan, Nihar R. Intrinsic Photoconductivity of few-layered ZrS2 Phototransistors via Multiterminal Measurements. Retrieved from https://par.nsf.gov/biblio/10142805. Semiconductor Science and Information Devices 1.2 Web. doi:10.30564/ssid.v1i2.1526.
Tanthirige, Rukshan M., Garcia, Carlos, Ghosh, Saikat, II, Frederick Jackson, Nash, Jawnaye, Rosenmann, Daniel, Divan, Ralu, Stan, Liliana, Sumant, Anirudha V., McGill, Stephen A., Ray, Paresh C., & Pradhan, Nihar R. Intrinsic Photoconductivity of few-layered ZrS2 Phototransistors via Multiterminal Measurements. Semiconductor Science and Information Devices, 1 (2). Retrieved from https://par.nsf.gov/biblio/10142805. https://doi.org/10.30564/ssid.v1i2.1526
Tanthirige, Rukshan M., Garcia, Carlos, Ghosh, Saikat, II, Frederick Jackson, Nash, Jawnaye, Rosenmann, Daniel, Divan, Ralu, Stan, Liliana, Sumant, Anirudha V., McGill, Stephen A., Ray, Paresh C., and Pradhan, Nihar R.
"Intrinsic Photoconductivity of few-layered ZrS2 Phototransistors via Multiterminal Measurements". Semiconductor Science and Information Devices 1 (2). Country unknown/Code not available. https://doi.org/10.30564/ssid.v1i2.1526.https://par.nsf.gov/biblio/10142805.
@article{osti_10142805,
place = {Country unknown/Code not available},
title = {Intrinsic Photoconductivity of few-layered ZrS2 Phototransistors via Multiterminal Measurements},
url = {https://par.nsf.gov/biblio/10142805},
DOI = {10.30564/ssid.v1i2.1526},
abstractNote = {We report intrinsic photoconductivity studies on one of the least examined layered compounds, ZrS2.Few-atomic layer ZrS2 field-effect transistors were fabricated on the Si/SiO2 substrate and photoconductivity measurements were performed using both two- and four-terminal configurations under the illumination of 532 nm laser source. We measured photocurrent as a function of the incident optical power at several source-drain (bias) voltages. We observe a significantly large photoconductivity when measured in the multiterminal (four-terminal) configuration compared to that in the two-terminal configuration. For an incident optical power of 90 nW, the estimated photosensitivity and the external quantum efficiency (EQE) measured in two-terminal configuration are 0.5 A/W and 120%, respectively, under a bias voltage of 650 mV. Under the same conditions, the four-terminal measurements result in much higher values for both the photoresponsivity (R) and EQE to 6 A/W and 1400%, respectively. This significant improvement in photoresponsivity and EQE in the four-terminal configuration may have been influenced by the reduction of contact resistance at the metal-semiconductor interface, which greatly impacts the carrier mobility of low conducting materials. This suggests that photoconductivity measurements performed through the two-terminal configuration in previous studies on ZrS2 and other 2D materials have severely underestimated the true intrinsic properties of transition metal dichalcogenides and their remarkable potential for optoelectronic applications.},
journal = {Semiconductor Science and Information Devices},
volume = {1},
number = {2},
author = {Tanthirige, Rukshan M. and Garcia, Carlos and Ghosh, Saikat and II, Frederick Jackson and Nash, Jawnaye and Rosenmann, Daniel and Divan, Ralu and Stan, Liliana and Sumant, Anirudha V. and McGill, Stephen A. and Ray, Paresh C. and Pradhan, Nihar R.},
}
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