Range Of Photodetectors Research Articles

Sn-based waveguide p-i-n photodetector with strained GeSn/Ge multiple-quantum-well active layer.

We report on Sn-based p-i-n waveguide photodetectors (WGPD) with a pseudomorphic GeSn/Ge multiple-quantum-well (MQW) active layer on a Ge-buffered Si substrate. A reduced dark-current density of 59 mA/cm2 was obtained at a reverse bias of 1V due to the suppressed strain relaxation in the GeSn/Ge active layer. Responsivity experiments revealed an extended photodetection range covering the O, E, S, C, and L telecommunication bands completely due to the bandgap reduction resulting from Sn-alloying. Band structure analysis of the pseudomorphic GeSn/Ge quantum well structures indicated that, despite the stronger quantum confinement, the absorption edge can be shifted to longer wavelengths by increasing the Sn content, thereby enabling efficient photodetection in the infrared region. These results demonstrate the feasibility of using GeSn/Ge MQW planar photodetectors as building blocks of electronic-photonic integrated circuits for telecommunication and optical interconnection applications.

Design and Modeling of GeSn-Based Heterojunction Phototransistors for Communication Applications

We propose the use of Ge $_{1-x}$ Sn $_x$ heterojunction phototransistors (HPTs) as efficient optical receivers on Si substrates and analyze their performance. Our designs use n-Ge/p-Ge $_{1-x}$ Sn $_x$ /n-Ge $_{1-x}$ Sn $_x$ layers pseudomorphically grown on Si wafers via a Ge virtual substrate, which offers compatibility with complementary metal–oxide–semiconductor (CMOS) technology. By incorporating Sn into the Ge photon-absorbing layer to shrink the bandgap, the photodetection range can be significantly extended to the mid-infrared (MIR) region with a considerably enhanced optical response. The use of HPT structures provides optical conversion gain to further enhance the optical responsivity, thereby enabling efficient photodetection in the short-wave infrared region. We develop theoretical models to calculate the composition-dependent band alignments, the band structures (by taking into account the nonparabolic effect), the absorption coefficient, and the optical responsivity for the proposed GeSn HPTs. As the Sn content increases, the conduction band nonparabolicity becomes increasingly significant and considerably impacts the optical absorption coefficient. Moreover, analysis of the spectral response for the Ge $_{1-x}$ Sn $_x$ HPTs shows that efficient photodetection covering the entirety of the fiber-optic telecommunication bands, as well as the emerging 2- $\mathbf {\mu }$ m MIR communication band, can be achieved. These results indicate that the proposed Ge $_{1-x}$ Sn $_x$ HPTs are attractive for use as high-responsivity CMOS-compatible photodetectors in communication applications.

High-Performance Photodetectors Using Transition Metal Dichalcogenide (TMD)-based Hybrid Structures

Since the era of graphene, atomically thin transition metal dichalcogenides (TMDs) with a two-dimensional (2D) semiconducting layered structure have recently received increasing attention as suitable materials for post-silicon electronics and optoelectronics due to their exceptional electrical, mechanical, and optical properties. Particularly, TMDs present different energy band gaps depending on the type of TMDs and also exhibit strong optical absorption and ultrafast charge transfer, thereby providing many opportunities for researches in various optoelectronic devices, including photodetectors, solar cells, and light-emitting diodes. However, despite their superior optical properties, it is difficult for TMDs to absorb sufficient light due to their atomically thin body thickness, consequently restricting the successful integration of TMD-based optoelectronic device applications. In this light, various studies have been performed to improve the characteristics of TMD-based optoelectronic devices (especially photodetectors) through their hybrid structure, by applying the doping[1] or absorbing[2] (with very high absorption rate) layers, or inserting a passivating[3] layer (with suppression of carrier scattering), eventually improving the collection of photo-generated carriers.Here, we demonstrate a high-performance TMD-based (WSe2 and ReSe2) photodetectors with a very high photoresponsivity (1.27×106 A/W for WSe2 and 1.18×106 A/W for ReSe2) and fast temporal photoresponse (rising/decaying time: 2.8/20.8 ms for WSe2 and 58/263 ms for ReSe2). This high-performance was accomplished by (i) applying a triphenylphosphine (PPh3)-based n-doping layer and (ii) inserting the passivating layers (hexagonal boron nitride (h-BN) or (3-aminopropyl)triethoxysilane (APTES) layers). The observed n-doping concentrations (Δn) were approximately 1.02 – 7.77×1011 cm-2 for TMD layers. By performing the PPh3-based n-doping process, the photoresponsivity of the TMD photodetectors increased (from 2.70×103 to 4.31×105 A/W for WSe2 and from 3.97×103 to 3.68×104 A/W for ReSe2). In particular, by additionally inserting a h-BN layer at the WSe2/SiO2 interface and an APTES layer at the ReSe2/SiO2 interface, we eventually obtained a very high photoresponsivity of 1.27×106 A/W for WSe2 and 1.18×106 A/W for ReSe2 while maintaining the other performance parameters (photoresponse times and photodetection range).[1] D.-H. Kang, J. Shim, S. K. Jang, J. Jeon, M. H. Jeon, G. Y. Yeom, W.-S. Jung, Y. H. Jang, S. Lee, J.-H. Park, ACS Nano 2015, 9, 1099.[2] S. H. Yu, Y. Lee, S. K. Jang, J. Kang, J. Jeon, C. Lee, J. Y. Lee, H. Kim, E. Hwang, S. Lee, J. H. Cho, ACS Nano 2014, 8, 8285.[3] S. Wang, X. Wang, J. H. Warner, ACS Nano 2015, 9, 5246.

Photodetectors: Broad Detection Range Rhenium Diselenide Photodetector Enhanced by (3‐Aminopropyl)Triethoxysilane and Triphenylphosphine Treatment (Adv. Mater. 31/2016)

The effects of triphenylphosphine (PPh3 ) and (3-amino-propyl)triethoxysilane (APTES) on a rhenium diselenide (ReSe2 ) photodetector are systematically studied by J.-H. Park and co-workers on page 6711 in comparison with a conventional MoS2 device. A very high performance ReSe2 photodetector is demonstrated, which has a broad photodetection range, high photoresponsivity (1.18 × 10(6) A W(-1) ), and fast photoswitching speed (rising/decaying time: 58/263 ms).

Broad Detection Range Rhenium Diselenide Photodetector Enhanced by (3-Aminopropyl)Triethoxysilane and Triphenylphosphine Treatment.

The effects of triphenylphosphine and (3-aminopropyl)triethoxysilane on a rhenium diselenide (ReSe2 ) photodetector are systematically studied by comparing with conventional MoS2 devices. This study demonstrates a very high performance ReSe2 photodetector with high photoresponsivity (1.18 × 10(6) A W(-1) ), fast photoswitching speed (rising/decaying time: 58/263 ms), and broad photodetection range (possible above 1064 nm).

Flexible transition metal dichalcogenide nanosheets for band-selective photodetection.

The photocurrent conversions of transition metal dichalcogenide nanosheets are unprecedentedly impressive, making them great candidates for visible range photodetectors. Here we demonstrate a method for fabricating micron-thick, flexible films consisting of a variety of highly separated transition metal dichalcogenide nanosheets for excellent band-selective photodetection. Our method is based on the non-destructive modification of transition metal dichalcogenide sheets with amine-terminated polymers. The universal interaction between amine and transition metal resulted in scalable, stable and high concentration dispersions of a single to a few layers of numerous transition metal dichalcogenides. Our MoSe2 and MoS2 composites are highly photoconductive even at bending radii as low as 200 μm on illumination of near infrared and visible light, respectively. More interestingly, simple solution mixing of MoSe2 and MoS2 gives rise to blended composite films in which the photodetection properties were controllable. The MoS2/MoSe2 (5:5) film showed broad range photodetection suitable for both visible and near infrared spectra.

Graphene photodetectors with ultra-broadband and high responsivity at room temperature

The ability to detect light over a broad spectral range is central to several technological applications in imaging, sensing, spectroscopy and communication. Graphene is a promising candidate material for ultra-broadband photodetectors, as its absorption spectrum covers the entire ultraviolet to far-infrared range. However, the responsivity of graphene-based photodetectors has so far been limited to tens of mA W(-1) (refs 5-10) due to the small optical absorption of a monolayer of carbon atoms. Integration of colloidal quantum dots in the light absorption layer can improve the responsivity of graphene photodetectors to ∼ 1 × 10(7) A W(-1) (ref. 11), but the spectral range of photodetection is reduced because light absorption occurs in the quantum dots. Here, we report an ultra-broadband photodetector design based on a graphene double-layer heterostructure. The detector is a phototransistor consisting of a pair of stacked graphene monolayers (top layer, gate; bottom layer, channel) separated by a thin tunnel barrier. Under optical illumination, photoexcited hot carriers generated in the top layer tunnel into the bottom layer, leading to a charge build-up on the gate and a strong photogating effect on the channel conductance. The devices demonstrated room-temperature photodetection from the visible to the mid-infrared range, with mid-infrared responsivity higher than 1 A W(-1), as required by most applications. These results address key challenges for broadband infrared detectors, and are promising for the development of graphene-based hot-carrier optoelectronic applications.

UV/vis range photodetectors based on thin film ALD grown ZnO/Si heterojunction diodes

We present ultraviolet–visible (UV/vis) range photodetectors (PDs) based on thin film ZnO (n)/Si (p) heterojunction diodes. ZnO films are grown by the atomic layer deposition (ALD) technique at growth temperatures of 80, 150, 200 and 250 ° C. The fabricated ZnO (n)/Si (p) photodetectors (ZnO–Si-PDs) show good electrical rectification characteristics with ON/OFF ratios reaching up to 103. Under UV (350 nm wavelength) and visible (475 nm wavelength) light illumination, the ZnO–Si-PDs give photoresponsivity values of 30–37 mA W−1 and 74–80 mA W−1 at 0.5 V reverse bias, respectively. Photoluminescence (PL) spectra of ALD grown ZnO thin films are used to support the results.

Drop‐cast and dye‐sensitized ZnO nanorod‐based visible‐light photodetectors

AbstractWe report the facile fabrication of metal–semiconductor–metal (MSM) photodetectors with dye‐sensitized ZnO nanorods (NRs) operating at wavelengths of ∼405–638 nm by a simple drop casting method. The ZnO NRs were synthesized by the hydrothermal synthesis method at 75 °C. The droplet of ethanol solution containing ZnO NRs was dropped between two metal electrodes and dried at 65 °C, which allows the ZnO NRs to be adhered and contacted to both metal electrodes. When a violet light of 405 nm was illuminated into the MSM ZnO NRs‐based photodetector, the photocurrent gain was obtained as ∼3.9 × 103 at the applied bias voltage of 5 V. By increasing the bias voltage from 10 V to 15 V, the device exhibited good recovery performance with a largely reduced reset time from 85.68 s to 2.47 s and an increased on–off ratio from 17.9 to 77.4. To extend the photodetection range towards the long visible spectral region, the ZnO NRs were sensitized by the N719 dye and then drop‐cast. The dye‐sensitized ZnO NRs‐based photodetector also exhibited good photocurrent switching under 638 nm of light illumination. (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Contribution of higher order plasmonic modes on optical absorption enhancement in amorphous silicon thin films

For an array of regularly patterned interacting spherical Ag nano particles over an amorphous silicon (a-Si:H) layer of thickness 200nm, we use Finite Difference Time Domain method for studying the plasmonic absorption enhancement within the a-Si:H layer over the visible range (400nm–750nm). The nano particle radius (R) has been varied from 100nm to 200nm and array period (D) from 320nm to 500nm satisfying the criteria 2R<D. Results show that when such a system is illuminated by a plane electromagnetic wave from the metal nano particles side the higher order plasmonic modes (mainly quadrupolar and octupolar) have significant contribution to the absorption enhancement within the a-Si:H layer. The role of the spectral overlap between different plasmonic modes has been described in controlling the absorption spectra for various configurations of R and D. It has been shown that a broad spectral absorption enhancement within the visible spectrum may be possible for a wide range of D variation from 320nm to 500nm using array of nano particles having R=140nm. On the other hand, choosing a surface coverage factor of 19%, enhanced absorption within narrow wavelengths bands has been observed. The position of these narrow bands may be tuned by suitable choice of nano particle size. We propose these findings to proffer promising applications in solar cells as also in visible range photo detectors.

The nonlinear microring add-drop filter

A new model is developed for the effects of the Kerr optical nonlinearity in a microring (racetrack) resonator coupled to input and output waveguides, which takes into account the nonlinearity in the couplers as well as the microring sections. It is shown how the nonlinear microring add-drop filter can be used as a self-adjusting all-optical beam splitter to extend the dynamic range of photodetectors and protect optoelectronic circuitry from high input powers.

Plasma-assisted molecular beam epitaxy of nitride-based photodetectors for UV and visible applications

Different growth modes have been identified in thick (⩾500 nm) AlGaN and InGaN layers grown by plasma-assisted molecular beam epitaxy as a function of parameters such as the growth temperature or the III–V ratio. Al mole fractions between 0% and 60% have been explored in AlGaN alloys, finding that a two-dimensional growth only occurs above a critical temperature under a metal-stable regime. This critical temperature increases with the Al content and depends strongly on the strain induced by the substrate and previous layers. A thermodynamical model is proposed to explain this behaviour. InGaN layers were also grown with In compositions in the 0–10% range. In this case, a metal-stable regime may induce In accumulation at the surface preventing the InGaN growth. Thus, slightly N-rich conditions are needed to reach an efficient In incorporation. To broaden the photodetection range of III-nitrides, photoconductors have been fabricated on both ternary alloys aiming to obtain high responsivity, solar-blind UV detectors (AlGaN) and narrow-band visible detectors (InGaN).

Zn3P2—a new material for optoelectronic devices

Abstract The fundamental optical and electronic parameters of Zn 3 P 2 are presented. Mg-Zn 3 P 2 structures are examined as solar energy converters and broad range photodetectors. A distinct photodichroism observed for junctions prepared on oriented single crystals is applied in light polarisation step indicators. Zn 3 P 2 thin films were obtained by vacuum evaporation and their optical properties were examined.

Zn3P2-a new material for optoelectronic devices

Abstract The fundamental optical and electronic parameters of Zn 3 P 2 are presented. MgZn 3 P 2 structures are examined as solar energy converters and broad range photodetectors. A distinct photodichroism observed for junctions prepared on oriented single crystals is applied in light polarization step indicators.

Application of epitaxial graded-gap semiconductor layers as broad range photodetectors

The trends in photodetector development and the properties of graded-gap semiconductors are briefly outlined, and the possibilities for the effective use of the graded-gap structure as a broad range IR and visible detector are presented.

A novel GaAs avalanche photodiode

A GaAs metal-semi-insulating-p-n+ structure is described as a novel reach-through avalanche photodiode. The p and n+ layers are simultaneously obtained by heat treatment and liquid-phase epitaxy. The high field at the p - n+ depletion layer allows one to reach multiplication factors close to 104 without avalanche breakdown. Photoinjected electrons from the metal barrier can extend the photodetection range up to 1.6 μm for Sn Schottky barriers.