Electronic structure of the PLD grown mixed phase MoS 2 /GaN interface and its thermal annealing effect

ACS Appl. Electron. Mater.

Pant

Chowdhury

et al. 2020

By combining unique properties of ultrathin 2D materials with conventional 3D semiconductors, devices with enhanced functionalities can be realized. Here, we report a selfpowered and ultrafast photodetector based on a hybrid MoS 2 / AlN/Si heterostructure. The heterojunction is formed by depositing a MoS 2 thin film by pulsed laser deposition on an AlN/Si(111) template. The vertical transport properties of the device under dark and light illumination conditions exhibit an excellent photoresponse in a broad range of wavelengths (300− 1100 nm) at 0 V. The maximum responsivity of this photodetector is found to be 9.93 A/W at a wavelength of 900 nm. The device shows an ultrafast temporal response with response/recovery times of 12.5/14.9 μs. X-ray photoelectron spectroscopy and crosssectional transmission electron microscopy reveal the presence of native oxygen impurities in AlN throughout the bulk of the film. These oxygen defects form a deep donor level in AlN and play a crucial role in the transport of the photogenerated carriers, resulting in enhanced device performance.

Section: Resultssupporting

confidence: 60%

“…A doublet (Δ ≈ 1.2 eV) in the S 2p spectrum is consistent with formation of MoS 2 . 45 Figure 3c shows the wide spectrum in which peaks corresponding to Mo, S, Al, and N can be seen. Thus, the XPS analysis corroborates the formation of MoS 2 on AlN/Si.…”

Section: Ev) a Weak Mo−o Peak Associated With Moomentioning

confidence: 99%

Defect-Mediated Transport in Self-Powered, Broadband, and Ultrafast Photoresponse of a MoS₂/AlN/Si-Based Photodetector

ACS Appl. Electron. Mater.

Pant

Chowdhury

et al. 2020

“…The spectra look similar to those reported earlier for GaN. 33,34 The position of the valence band maxima (VBM) is calculated to be 2.1 ± 0.1 eV, depicting n-type conductivity. We have also taken the spectra with different emission angles to investigate the surface Fermi-level (E F ) pinning (not shown).…”

Section: ■ Results and Discussionsupporting

confidence: 84%

Solution-Processed-2D on 3D Heterojunction UV–Visible Photodetector for Low-Light Applications

Kumar

Prakash

ACS Appl. Electron. Mater.

et al. 2019

Self Cite

We have demonstrated a heterojunction photodetector (PD) based on reduced graphene oxide (r-GO) and metal−organic chemical vapor deposition (MOCVD)-grown gallium nitride (GaN) that can sense very low light intensities in the above-band-gap and below-band-gap regimes, showing no and high photoconductive gains, respectively. The current− voltage characteristics of the device transforms from quasi photoconductive to photodiode behavior once the illumination wavelength is in the below-band-gap regime. The device exhibits a very low dark current of 0.85 pA at zero bias. In the selfpowered mode with low-light conditions (∼0.38 μW/cm 2 ) at 360 nm illumination, the light-to-dark current (I Light /I Dark ) ratio, responsivity (R λ ), specific detectivity (D*), and external quantum efficiency (EQE) of the fabricated PD were calculated to be ∼1 × 10 4 , 0.22 A/W, 1.486 × 10 14 Jones (cm Hz 1/2 W −1 ), and 77%, respectively. The response and recovery time of the PD were typically 485 and 886 μs, respectively under 280 Hz light switching frequency at zero bias. The device also shows significant photoconductive response with a typical persistent photoconductivity behavior at an applied bias of 5 V with extremely large I Light /I Dark ratio of ∼10 7 at 360 nm (∼0.15 mW/cm 2 ). The R λ , D*, and EQE were found to be 529 A/W, 4.25 × 10 16 Jones, and ∼2 × 10 5 %, respectively, for 360 nm illumination under low-light conditions (∼0.38 μW/cm 2 ), at 5 V applied bias. The extraordinary performance of the device in both photovoltaic and photoconductive modes makes r-GO/GaN heterojunction scheme suitable for dual-mode low-light UV−visible applications.

“…Figure shows the Ga 3d spectra, VBM, schematic band diagram, C 1s and O 1s core level intensity measured with different emission angles on GaN surface. In order to estimate the different compositions associated with the Ga 3d region in GaN sample, we have carefully fitted all the spectra with four different components . The main peak represents the contribution from the GaN bonds exhibiting a doublet corresponding to Ga 3d 5/2 and 3d 3/2 at the binding energy values of 19.5 and 20.0 eV, respectively.…”

Section: Resultsmentioning

confidence: 99%

Long‐Term, High‐Voltage, and High‐Temperature Stable Dual‐Mode, Low Dark Current Broadband Ultraviolet Photodetector Based on Solution‐Cast r‐GO on MBE‐Grown Highly Resistive GaN

Prakash

Kumar

Advanced Optical Materials

et al. 2019

Self Cite

materials to form heterostructures due to the improved functionality of electronic and optoelectronic devices. [1][2][3][4][5][6] The 2D material-based devices can have a revolutionizing impact on technology covering from vacuum photodetection and photovoltaics to optical modulators and high speed data communication. [7][8][9][10][11][12][13][14][15][16] Predominantly through vertical transport of photogenerated carriers, the hybrid structures allow us to overcome the inherent persistent photoconductivity (PPC), where photocurrent of the host material generally persists for a long duration even after the illumination is removed, generally observed in the compound III-nitride semiconductor materials. [17][18][19][20][21] Usually PPC occurs due to the presence of donor and acceptor states closer to the conduction band minimum (CBM) and valence band maximum (VBM), which provides a large number of electron and hole trap states in the host material, respectively. Alternatively, with an introduction of intrinsic semiconductor materials, the PPC could be reduced as the donor and acceptor states show a shift from the CBM and VBM edges toward the midgap positions, which facilitate fast recombination time in comparison to the transit time of photo generated carriers through host materials. This has resulted in high speed operation in photoconductive mode. [22] In particular, GaN integrated with reduced-graphene oxide (r-GO) is a promising heterostructure for achieving improved device characteristics such as low dark current, high spectral responsivity, and high response speed. [17] 2D r-GO makes an optically active heterojunction with GaN. The emphasis so far has been given on r-GO/GaN heterostructure operating in the photovoltaic mode where the photogenerated carriers are swiftly swept across the depletion region predominantly via vertical transport. However, in the photoconductive mode operation, where the photogenerated carriers traverse across the host materials under the influence of an external bias exceeding the built-in-field of the heterostructure device, suffers either from high leakage current and/or PPC due to inherently negatively charged defects rich GaN. [23] The intentional/unintentional doping of suitable species can cause compensation of free New generation of hybrid photodetectors may provide the optimal solution for compact, highly sensitive, durable, and reliable broadband ultraviolet (BUV) sensors. A high-performance dual-mode BUV photodetector based on melding of highly resistive GaN and reduced graphene oxide is reported. Under zero bias, the device exhibits a sub-picoampere dark current, high light-to-dark current (I Light /I Dark ) ratio of ≈3.8 × 10 3 and high BUV-visible rejection ratio (≈1.8 × 10 2 ) with fast rise and fall times. The photodetector displays remarkable stability when subject to extreme operating conditions. The photoresponse of the detector shows a dark current of ≈2.41 nA at ± 200 V bias, I Light /I Dark ratio of ≈200 and high BUV-vis rejection ratio (≈7 × 10 2 ). The response ...