Quantum Efficiency Of Devices Research Articles

Electronic and optical properties of Be2C/graphene heterojunction from first-principles calculations

We study the electrical and optical properties of the van der Waals (vdW) heterojunction Be2C/graphene by first principles. The constructed heterojunction exhibits p-type Ohmic contact. It is found that the varied interlayer distance and biaxial stress can influence the electronic structure and charge transfer of heterojunction. While the small variety of the difference of electrostatic potential of the heterojunction induces the small change of charge transfer at the contact interface, so the p-type Ohmic contact can still be formed. Meanwhile, the decreased interlayer distance and tensile strain can enhance the optical absorption of heterojunction. Then we calculate the external quantum efficiency of the optoelectronic device based on Be2C/graphene that reaches to 27.8%. This work provides a way to design electronic and optoelectronic devices based on Be2C/graphene in the future.

Two Novel Neutral Cyclometalated Iridium(III) Complexes Based on 10,11,12,13-Tetrahydrodibenzo[a,c]phenazine for Efficient Red Electroluminescence.

Two novel neutral phosphorescent iridium(III) complexes (Ir1 and Ir2) were rationally designed and synthesized with high yields using 10,11,12,13-tetrahydrodibenzo[a,c]phenazine as the main ligand. The two complexes showed bright-red phosphorescence (625 nm for Ir1, and 620 nm for Ir2, in CH2Cl2), high-luminescence quantum efficiency (0.32 for Ir1, and 0.35 for Ir2), obvious solvatochromism and good thermostability. Then, they were used to fabricate high-efficiency red OLEDs via vacuum evaporation; the maximum current efficiency, power efficiency, and external quantum efficiency of the red devices based on Ir1 and Ir2 are 13.47/15.22 cd/A, 10.35/12.26 lm/W, and 10.08/7.48%, respectively.

Optoelectronic properties of quasi-two-dimensional perovskite light-emitting diodes via poly(9-vinylcarbazole) interlayer modification

Perovskite light-emitting diodes (PeLEDs) have attracted much attention due to their excellent performance. In this work, phenylethylamine bromide (PEABr) was employed to modify perovskite phases, while Poly(9-vinylcarbazole) (PVK) was added as a hole transport layer between perovskite and PEDOT:PSS to engineer the device structure, which is predicted to improve the optoelectronic performance of PeLEDs synergistically. The doping of PEABr in MAPbBr3 can improve the radiative recombination of the emission layer through the formation of two-dimensional perovskite phases and modified film morphology. When the ratio of MAPbBr3:PEABr is 1:0.25, the maximum luminance of the optimal device increased from 80 to 9000 cd/m2 and the maximum external quantum efficiency increased from 0.02% to 1.63% compared with the control device without PEABr doping. In addition, the hole injection ability of the device is further improved by adding PVK as the hole transport layer. The introduction of PVK can also facilitate the interface modification via surface defect passivation. When the PVK concentration is 10 mg/ml, the maximum current efficiency and external quantum efficiency of the optimal device are increased to 13.70 cd/A and 2.70%, respectively. These findings can provide a basis for the enhanced performance of PeLEDs.

High-performance 2D WS2 photodetector enhanced by charge-transfer doping through NH3 annealing

Transition metal dichalcogenides (TMDs) are potential candidates towards the next-generation photodetector, owing to their tunable energy bandgap and strong light–matter interaction. However, the low charge-carrier mobility and insufficient quantum efficiency of TMDs-based devices restrain their optoelectronic performances. Therefore, an effective and facile doping method needs to be developed for overcoming their poor optoelectronics properties. Here, we demonstrate a controllable nondegenerate n-doping technique for 2D TMDs materials by annealing under NH3 flow. The on/off current ratio and field-effect mobility of the device after annealing treatment increases about 2 orders of magnitude and 23 times, respectively. We attribute this remarkable doping effect to the physical adsorption and chemical adsorption of NH3 as well as the associated formation of isolated sulfur vacancies, which is dynamically activated during the annealing treatment, and further verified by the atomic-scale characterization and density functional theory calculations. The annealing temperature and time present a controllable modulation on the electron doping levels of the WS2 channel. The fabricated WS2 photodetector can operate in a broad range of visible light at room temperature. At 532 nm wavelength, the responsivity of 2.97 A/W, external quantum efficiency of 699% and specific detectivity of over 1010 Jones indicate its great potential in sensitive and power-efficient photodetectors. Our results provide an effective method to realize controllable n-doping of 2D materials, aiming for fabricating high-performance 2D photodetectors.

Deep red donor-acceptor type thermally activated delayed fluorescence emitter with o-carborane as an acceptor

o-Carborane is a strong acceptor having a three-dimensional structure of 10 borons and 2 carbons. Thus, this study explores the potential of using o-carborane as a new acceptor in designing donor-acceptor (D-A) type thermally activated delayed fluorescence (TADF) materials. Accordingly, a D-A type TADF emitter was designed using o-carborane as an acceptor and 9,9-dimethyl-9,10-dihydroacridine as a donor. The TADF emitter exhibited deep red emission with a peak wavelength of 642 nm as proven by delayed fluorescence in the transient photoluminescence analysis. Deep red emission with a peak wavelength of 651 nm was also observed in both doped and non-doped devices, as demonstrated using electroluminescence devices. Finally, the maximum external quantum efficiency of DMAC-oCB devices was found to be 5.2% in the doped device and 2.1% in the non-doped device.

Non-monotonic current dependence of intersystem crossing and reverse intersystem crossing processes in exciplex-based organic light-emitting diodes

Intersystem crossing (ISC) and reverse ISC (RISC) between singlet and triplet polaron-pair and exciplex state are important spin-mixing processes in exciplex-based organic light-emitting diodes (EB-OLEDs). These two processes usually show normal current dependence which weakens with the increase of bias-current. This is because the bias-current increases by improving the device bias-voltage. When the bias-voltage rises, the electric field within the device is enhanced, which facilitates the electric-field-induced dissociation of polaron-pair and exciplex states and then reduces their lifetime. That is, less polaron-pair and exciplex states participate in the ISC process and RISC process, leading these two processes to weaken. Here, magneto-electroluminescence (MEL) is used as a fingerprint probing tool to observe various current-dependent ISC and RISC processes in EB-OLEDs with different charge balances via modifying the device hole-injection layer. Interestingly, current-dependent MEL traces of the unbalanced device display a conversion from normal ISC (1–25 μA) process to abnormal ISC (25–200 μA) process, whereas those of the balanced device show conversions from normal ISC (1–5 μA) into abnormal RISC (10–50 μA) and then into normal RISC (50–150 μA) and finally into abnormal ISC (200–300 μA) process. By fitting and decomposing the current-dependent MEL traces of the unbalanced and balanced devices, we find that the ISC process and RISC process in these two devices first increase then decrease as the bias-current increases. These non-monotonic current-dependent ISC process and RISC process are attributed to the competition between the increased number and the reduced lifetime of polaron-pair state and exciplex state during improving the bias-current. Furthermore, the RISC process in the balanced device is stronger than that in the unbalanced device. This is because the balanced carrier injection can facilitate the formation of triplet exciplex states and weaken the triplet-charge annihilation (TQA) process between triplet exciplex states and excessive charge carriers, which leads the number of triplet exciplex states to increase. That is to say, more triplet exciplex states can be converted into singlet exciplex states through the RISC process, causing the external quantum efficiency of the balanced device to be higher than that of the unbalanced device. Obviously, this work not only deepens the understandings of current-dependent ISC and RISC processes in EB-OLEDs, but also provides an insight into the device physics for designing and fabricating high-efficiency EB-OLEDs.

Study of the Interfacial Oxidation of InP Quantum Dots Synthesized from Tris(dimethylamino)phosphine.

InP quantum dots (QDs) are the most competitive in terms of environmentally friendly QDs. However, the synthesis of InP QDs requires breakthroughs in low-cost and safe phosphorus precursors such as tri(dimethylamino)phosphine [(DMA)3P]. It is found that even if the oxygen is completely avoided, there are still oxidation state defects at the core/shell interface of InP QDs. Herein, the record-breaking (DMA)3P-based red InP QDs were synthesized with the assist of HF processing to eliminate the InPOx defect and improve the fluorescence efficiency. The maximum photoluminescence quantum yield was 97.7%, which is the highest of the red InP QDs synthesized by the aminophosphine. The external quantum efficiency and brightness of the QD light-emitting diode device are also improved accordingly from 0.6% and 1276 cd·m-2 to 3.5% and 2355 cd·m-2, respectively.

Performance Analysis of Ultrathin Cu(In,Ga)Se2 Solar Cells with Backwall Superstrate Configuration Using AMPS-1D

This study used AMPS-1D to peform numerical simulations and model the behavior of back-wall superstrate solar cells based on Cu(In,Ga)Se2 (CIGS) thin films to investigate optimal conditions and obtain maximum efficiency. The effects of absorber thickness and density of interface defects were examined along with the work function of the transparent conductive oxide (WTCO) to investigate their influence on the output parameters. Measurements of device performance (J-V) and Quantum Efficiency (QE) showed that the performance of the cell improved as the thickness of the CIGS layer decreased because photons were absorbed near the junction. The device achieved an efficiency of 16.4% using an optimal thickness for the CIGS layer on the order of 0.3µm, defect densities in the range of 1013-1015cm-3, doping concentration of the n-TCO back contact on the order of 1019cm-3, and WTCO in the range of 4.5-5.2eV. These results show that the generated electron-hole pairs had a high probability of separation and demonstrate the potential of this device structure.

Radiative Recombination and Carrier Injection Efficiencies in 265 nm Deep Ultraviolet Light‐Emitting Diodes Grown on AlN/Sapphire Templates with Different Defect Densities

The electro‐optical characteristics of deep ultraviolet light‐emitting diodes (DUV LEDs) emitting at 265 nm and grown on AlN/sapphire templates with different threading dislocation densities, i.e., high‐temperature annealed (HTA) AlN, epitaxially laterally overgrown (ELO) AlN, and HTA‐ELO AlN are analyzed. The external quantum efficiency of each individual device is separated into maximum radiative recombination efficiency, carrier injection efficiency, and light extraction efficiency. This is achieved by combining an ABC‐model‐based fit of the current‐dependent external quantum efficiency together with calibrated Monte Carlo ray‐tracing simulations. A maximum radiative recombination efficiency between 50% and 60% is estimated for DUV LEDs grown on ELO and HTA‐ELO AlN/sapphire, whereas the values for devices grown on HTA AlN/sapphire are around 45%. The extracted radiative recombination efficiency does not scale with the measured threading dislocation density (TDD), even when accounting for the inhomogeneous TDD in the AlN base layers. This discrepancy is attributed to the formation of dislocation half‐loops introduced by additional compressive strain caused by the HTA process and may result in the formation of additional nonradiative recombination centers in the AlGaN multi‐quantum well region. In addition, the carrier injection efficiency values ranging from 45% to 55% are determined for devices grown on all three templates.

Spirobifluorene-based hole-blocking material with enhanced efficiency through hole and exciton confinement in blue fluorescent OLEDs

A new hole-blocking material, 2-(9,9′-spirobi[fluoren]-5-yl)-4-phenylbenzo [4,5]thieno[3,2-d]pyrimidine (SBF-BTPym), was designed and synthesized using spirobifluorene and electron transport moieties. The high triplet energy and high thermal stability of the spirobifluorene moiety were suitable for designing the hole-blocking material for blue fluorescent organic light-emitting diodes (OLEDs). The electron deficiency of benzothienopyrimidine allowed good electron transport properties, and a deep highest occupied molecular orbital energy level of −6.55 eV suppressed leakage of the holes from the emitting layer (EML) to the adjacent layer. Blue fluorescent OLEDs consisting of a triplet-triplet annihilation–induced host were fabricated using SBF-BTPym. The maximum external quantum efficiency of the blue fluorescent device was 7.2%, which was higher than that of the device without a hole-blocking layer by 10%. According to transient electroluminescence analysis, exciton confinement in the EML is mainly responsible for the improved efficiency.

Enhanced optoelectrical performance of ultraviolet detectors based on self-assembled porous zinc oxide nanostructures

A templated self-assembly technique was utilized in the present study to grow porous zinc oxide nanostructures. The nanostructures were formed by the electrochemical deposition of ZnO through the interstitial spaces between polymer microsphere templates. After the deposition, polymer microspheres were removed by dissolving in chloroform solvent, leaving porous ZnO nanostructures. This technique is benefited from facile controllability of the pore morphology and size by varying the diameter of microspheres. X-ray diffraction analysis showed a dominant peak corresponding to the hexagonal ZnO structure. Moreover, no significant structural strain was observed after the removal of spheres unlike the other synthesis methods of porous materials. The improved photoluminescence (PL) properties revealed an enhancement in the light capturing capability of the systems due to the multiple scattering of light in the pore walls. The porous sample showed a PL blue-shift compared to the flat one, indicating a reduction in crystallite size of ZnO nanostructures. To assess the photonic applications of synthesized porous ZnO substrates, a metal-semiconductor-metal photodetector was developed via the metallization of ZnO nanostructures, and their optoelectrical properties were tested under UV radiation. The results showed an improvement in photosensitivity and quantum efficiency of devices based on porous ZnO substrates which can be assigned to the larger exposed area and elevated rates of electron-hole generation in this sample.

Influence of Light-Matter Interaction on Efficiency of Quantum-Dot Light-Emitting Diodes.

Light-matter interaction can affect the radiative decay rate of excitons and thus the emission quantum yield (QY) of quantum dots (QDs). In this work, light-matter interaction and outcoupling efficiency of QD light-emitting diodes with different structures are investigated experimentally and theoretically. We show that the external quantum efficiency (EQE) of top-emitting devices is higher than that of the bottom-emitting devices, which is mainly due to the stronger light-matter interaction and higher light outcoupling efficiency of the top-emitting structures. In addition, we show that the QY enhancement induced by light-matter interaction is more significant for low-QY QDs. Our results suggest that top-emitting structures are more powerful for improving the EQE of devices built with low-QY QDs.

Fine Tuning the Energetics of 2-(2′-Hydroxyphenyl)oxazoles to Obtain Highly Efficient Organic White-Light-Emitting Devices

By using the strategy of fine-tuning the energetics to explore single-molecule white materials with reversible excited-state intramolecular proton transfer (ESIPT), compound 4′-(di-p-tolylamino)-3-(5-(4′-(diphenylamino)-[1,1′-biphenyl]-4-yl)oxazol-2-yl)-5-methyl-[1,1′-biphenyl]-4-ol (2a) has been synthesized and then fabricated as organic white-light-emitting devices. The rhodium-catalyzed C–H activation reaction offers an effective method to construct the white-emitting molecules. The 2a-based devices display white electroluminescence with white region CIE coordinates, which is the first reported organic white-light-emitting device (WOLED) based on the single-molecule 2-(2′-hydroxyphenyl)oxazoles with a reversible ESIPT equilibrium. The external quantum efficiency (EQE) of the white-light device reached 6.3%, achieving the highest EQE in the single-molecular cold WOLEDs using an ESIPT material as the emitter. Furthermore, the hybridized local charge transfer (HLCT)-state feature of 2a has been confirmed by a fluorescence test and density functional theory (DFT) calculations. The result shows the first example of single-molecule cold WOLEDs with HLCT material.

Analysis of Hole Transport Layer and Electron Transport Layer Materials in the Efficiency Improvement of Sb2(Se1−xSx)3 Solar Cell

Sb2(Se1−x S x )3 compounds have been regarded as an excellent absorber in thin film solar cells processing. At present, the best efficiency reported in these chalcogenides of antimony corresponds to FTO/CdS/Sb2(Se1−x S x )3/Spiro‐OMeTAD/Au structure with 10.5%. Herein, a comparative study on the Sb2(Se1−x S x )3 solar cell performance with different electron transport layers (ETLs) and hole transport layers (HTLs) is carried out. The main photovoltaic parameters such as short‐circuit current density, open‐circuit voltage, fill factor, power conversion efficiency, and external quantum efficiency of devices with n–i–p structures are analyzed from a theoretical point of view. The impact of different ETL, HTL, and absorber thicknesses as well as the influence of Sb2(Se1−x S x )3 bulk and interface defects on the final efficiency of the device is investigated. After the optimization of the above physical parameters, it is demonstrated that with the FTO/ETL/Sb2(Se1−x S x )3/HTL/Au proposed structure, efficiency can be improved from 10% to 16%. In particular, it is found that Cd0.6Zn0.4S and ZnO are better candidates for ETL, while the use of NiO and Cu2O as HTL results in increased efficiencies in comparison to the traditional Spiro‐OMeTAD.

Highly efficient tandem OLED based on a novel charge generation layer of HAT-CN/CuPc heterojunction

A novel non-doped organic heterojunction (OHJ) composed of HAT-CN and CuPc is proposed to be charge generation layers (CGL) for constructing high efficiency tandem organic light-emitting diodes (OLEDs). The highest current efficiency and external quantum efficiency (EQE) of tandem device with this CGL are 46.3 cd/A and 15.1%, which are 125% and 107% higher than those of single emissive unit OLED, respectively. Furthermore, the tandem device provides better stability. The efficiency roll-off from the maximum to 1000 cd/m2 is 7.2% for the tandem device, which delivers a great improvement compared to that of single emissive unit OLED (21.9%). And CuPc thickness in CGLs merely slightly affects the device performance, because of the tradeoff between improved charge injection and declined transmittance with the increase of the CuPc thickness. The experimental results demonstrate that the organic heterojunction consisting of HAT-CN/CuPc is a feasible CGL for developing high performance tandem OLEDs.

Exciton harvesting of dual-emitting room temperature organic phosphors using a thermally activated delayed fluorescence sensitizer

Efficiency improvement of dual-emitting room-temperature phosphorescent (RTPH) organic light-emitting diodes (OLEDs) was studied by employing a device approach of sensitizing the RTPH emission using a thermally activated delayed fluorescence (TADF) sensitizer by energy transfer mechanism. The RTPH material was (10-phenyl-10H-phenoselenazine-3,7-diyl)bis(phenylmethanone) (PSeBBz) which emits at 505 nm by TADF and 563 nm by phosphorescence. The luminance and maximum external quantum efficiency of the PSeBBz device were enhanced by about 4.0 times and 1.7 times by the TADF sensitizing approach, respectively. Transient photoluminescence and transient electroluminescence measurements revealed that the long-time scale emission components of the dual-emitting RTPH material by triplet excitons were enhanced, indicating that exciton population was increased by sensitized Förster energy transfer and reduced triplet exciton quenching process such as triplet-triplet annihilation and triplet-polaron annihilation. • Efficiency enhancement of dual-emitting room-temperature phosphorescent organic light-emitting diode. • Phosphor sensitization using thermally activated delayed fluorescence materials. • Reduced triplet exciton quenching mechanisms using sensitizing device approach.

Designing the optoelectronic properties of BODIPY and their photovoltaic applications for high performance of organic solar cells by using computational approach

A series of four novel pi-conjugated chromophores named BDP1-BDP4 have been designed in quest to enhance the PCE of organic photovoltaic cells. These chromophores were developed by using 4,4-difluroboradiaza-s-indacene (BODIPY) as a core, Triphenylamine (TPA) as donor and different end-capped acceptors i.e., 2-ethylidene malononitrile (BDP1), methyl-2-cyanobut-2-enoate (BDP2), 4-ethylidene-2-methyl-5-thiooxoisothiazolidin-3-one (BDP3), 2-(2-ethylidene-5,6-difluoro-3-oxo-2,3-dihydroinden-1-ylidene) malononitrile (BDP4). DFT and TD-DFT approach using B3LYP functional was employed to assess the photophysical, as well as opto-electronic properties of designed chromophores BDP1-BDP4. FMOs and Transition Density Matrix evaluations were executed to get insights about charge distribution, chemical reactivity, and stability of all molecules under investigation. Exciton binding energy and reorganization energy values have been computed to investigate exciton dissociation and charge carrier mobilities, respectively. All the newly developed molecules exhibit reduced band gap, red shift absorption bands, low exciton binding energy, small reorganization energy values and moderate Voc value in comparison to reference molecule which demonstrate that these newly developed molecules can be utilized as favorable photovoltaic materials. BDP4 considered to be promising acceptor molecule with highest λmax (883 nm), narrow band gap (1.22eV) and lowest λe value (0.01136). This theoretical and computational study revealed that the designed chromophores could be employed as efficient acceptors, in order to upsurge the quantum efficiency of organic photovoltaic devices.

Semi-transparent, high-performance lead-free Cs3Bi2I9 single crystal self-driven photodetector

All-inorganic Bi-based perovskites have attracted much attention due to their excellent stability, environmentally friendly, and low-cost solution processability. However, due to the large exciton binding energy and small light absorption coefficient, the performance of the Bi-based perovskite photodetector (PD) is far behind of the traditional Pb-based perovskite PDs. In this work, the lead-free all-inorganic Cs3Bi2I9 (CBI) perovskite single crystal was synthesized by a space-confined antisolvent-assisted crystallization method for high-performance, semi-transparent, and self-driven PDs with an ITO/SnO2/CBI/PTAA/Au/ITO structure. Electrical and optical properties of Au/ITO transparent electrode were studied considering its figure of merit and device quantum efficiency through optimizing the Au thickness. Finally, our optimized semi-transparent device showed excellent self-driven performance with a large on/off ratio of ∼5700, a high responsivity of 52.06 mA/W, a high detectivity of >1012 Jones, and a large linear dynamic range of up to 140.7 dB. In addition, our device demonstrated excellent characteristics to the weak light detection and the long-term stability. The Au/ITO electrode was adopted and tailored to balance the device performance and transparency, which provides a good route for developing high-performance and transparent devices in the future.

Origin of the discrepancy between the fundamental and optical gaps and native defects in two dimensional ultra-wide bandgap semiconductor: Gallium thiophosphate

Ultra-wide bandgap (UWBG) semiconductors have great potential for high-power electronics, radio frequency electronics, deep ultraviolet optoelectronic devices, and quantum information technology. Recently, the two-dimensional UWBG GaPS4 was first applied to the solar-blind photodetector in experiments, which was found to have remarkable performance, such as high responsivity, high quantum efficiency, etc., and promising applications in optoelectronic devices. However, the knowledge of monolayer (ML) GaPS4 for us is quite limited, which hinders its design and application in optoelectronic devices. Here, we focus on the properties of electronic structure and intrinsic defects in ML GaPS4 by first-principles calculations. We confirmed that the fundamental gap of ML GaPS4 is 3.87 eV, while the optical gap is 4.22 eV. This discrepancy can be attributed to the inversion symmetry of its structure, which limits the dipole transitions from valence band edges to conduction band edges. Furthermore, we found that intrinsic defects are neither efficient p-type nor n-type dopants in ML GaPS4, which is consistent with experimental observations. Our results also show that if one expects to achieve p-type ML GaPS4 by selecting the appropriate dopant, P-rich conditions should be avoided for the growth process, while for achieving n-type doping, S-rich growth conditions are inappropriate. This is because due to the low strain energy, PS(c)+ has very low formation energy, which leads to the Fermi levels (EF) pinning at 0.35 eV above the valence band maximum and is not beneficial to achieve p-type ML GaPS4 under the P-rich conditions; the large lattice relaxation largely lowers the formation energy of SGa−, which causes the EF pinning at 0.72 eV below the conduction band minimum and severely prevents ML GaPS4 from being n-type doping under the S-rich conditions. Our studies of these fundamental physical properties will be useful for future applications of ML GaPS4 in optoelectronic devices.

Local Avalanche Effect of 4H-SiC p-i-n Ultraviolet Photodiodes With Periodic Micro-Hole Arrays

In this report, 4H-SiC p-i-n photodiodes with various micro-hole arrays are fabricated, then measured and discussed by using photoelectric measurement system and simulation software. Periodic micro-hole arrays etched from p layer to i layer are obtained by using the selective etching technology, which increases the photosensitive area of devices and reduces the ultraviolet light absorption of p layer. The average dark current of devices has an ultralow value of approximate <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$6.0\times 10 ^{-15}$ </tex-math></inline-formula> A in the low reverse bias range of 0–10 V. Furthermore, the device with <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$4 ~\mu \text{m}$ </tex-math></inline-formula> micro-hole exhibits the best performance and its peak responsivity increased by 10.4 % compared to the conventional device. It is significant that the peak responsivity and corresponding external quantum efficiency of devices with <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$4 ~\mu \text{m}$ </tex-math></inline-formula> micro-hole at 40 V bias are 815 % and 819 % higher than those of devices without micro-hole, respectively. This is attribute to the fact that a high electric field is observed around the micro-holes as the reverse bias increased to 40 V, which leads to local avalanche. Thus, the local avalanche photodiodes work at a relatively low bias, which improved the responsivity and quantum efficiency of the device enormously.