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122 results on '"You-Dou Zheng"'

1. High-Performance Semi-Polar InGaN/GaN Green Micro Light-Emitting Diodes

Author

Fei-Fan Xu, Tao Tao, Bin Liu, Xuan Wang, Mao-Gao Gong, Ting Zhi, Dan-Feng Pan, Zi-Li Xie, Yu-Gang Zhou, You-Dou Zheng, and Rong Zhang

Subjects
III-nitrides, semi-polar, micro-LEDs, InGaN/GaN, green., Applied optics. Photonics, TA1501-1820, Optics. Light, QC350-467
Abstract

Semi-polar micro-LEDs have gain increasing interests due to the advantages of polarization control and quantum efficiency improvement. In this work, a novel semi-polar (20-21)-plane micro-LEDs array has been designed and manufactured. In comparison with c-plane micro-LEDs, semi-polar micro-LEDs indicate better electrical and optical performance. The relative EQE of semi-polar micro-LEDs remains at 62% under the injected current density of 775.6 A/cm2, which indicates a reduced efficiency droop due to less polarization in MQWs. It has been further proved by a significant reduction of 55% in emission peak blue-shift under the injected current density from 11.1 A/cm2 to 775.6 A/cm2. In addition, the carrier recombination dynamics and spatial light distribution of semi-polar micro-LEDs with different pixel sizes have been studied. Fast recombination lifetime in smaller size semi-polar micro-LEDs indicates a promising way to be used as a high modulation bandwidth light source. Stable and uniform light distribution in a wider range of spatial azimuths further supports for the semi-polar micro-LEDs as a strong candidate for the applications of high-resolution display and high-speed visible light communication.

Published
2020
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2. Suppression and compensation effect of oxygen on the behavior of heavily boron-doped diamond films

Author

Li-Cai Hao, Zi-Ang Chen, Dong-Yang Liu, Wei-Kang Zhao, Ming Zhang, Kun Tang, Shun-Ming Zhu, Jian-Dong Ye, Rong Zhang, You-Dou Zheng, and Shu-Lin Gu

Subjects
General Physics and Astronomy
Abstract

This work investigates the suppression and compensation effect of oxygen on the behaviors and characteristics of heavily boron-doped microwave plasma chemical vapor deposition (MPCVD) diamond films. The suppression effect of oxygen on boron incorporation is observed by an improvement in crystal quality when oxygen is added during the diamond doping process. A relatively low hole concentration is expected and verified by Hall effect measurements due to the compensation effect of oxygen as a deep donor in diamond. A low acceptor concentration, high compensation donor concentration and relatively larger acceptor ionization energy are then induced by the incorporation of oxygen; however, a heavily boron-doped diamond film with high crystal quality can also be expected. The formation of an oxygen–boron complex structure instead of oxygen substitution, as indicated by the results of x-ray photoelectron spectroscopy, is suggested to be more responsible for the observed enhanced compensation effect due to its predicted low formation energy. Meanwhile, density functional theory calculations show that the boron–oxygen complex structure is easily formed in diamond with a formation energy of –0.83 eV. This work provides a comprehensive understanding of oxygen compensation in heavily boron-doped diamond.

Published
2023

3. Effect of oxygen on regulation of properties of moderately boron-doped diamond films

Author

Dong-Yang Liu, Li-Cai Hao, Wei-Kang Zhao, Zi-Ang Chen, Kun Tang, Shun-Ming Zhu, Jian-Dong Ye, Rong Zhang, You-Dou Zheng, and Shu-Lin Gu

Subjects
General Physics and Astronomy
Abstract

Regulation of oxygen on properties of moderately boron-doped diamond films is fully investigated. Results show that, with adding a small amount of oxygen (oxygen-to-carbon ratio < 5.0%), the crystal quality of diamond is improved, and a suppression effect of residual nitrogen is observed. With increasing ratio of O/C from 2.5% to 20.0%, the hole concentration is firstly increased then reduced. This change of hole concentration is also explained. Moreover, the results of Hall effect measurement with temperatures from 300 K to 825 K show that, with adding a small amount of oxygen, boron and oxygen complex structures (especially B3O and B4O) are formed and exhibit as shallow donor in diamond, which results in increase of donor concentration. With further increase of ratio of O/C, the inhibitory behaviors of oxygen on boron leads to decrease of acceptor concentration (the optical emission spectroscopy has shown that it is decreased with ratio of O/C more than 10.0%). This work demonstrates that oxygen-doping induced increasement of the crystalline and surface quality could be restored by the co-doping with oxygen. The technique could achieve boron-doped diamond films with both high quality and acceptable hole concentration, which is applicable to electronic level of usage.

Published
2022

4. An ultra-sensitive and selective nitrogen dioxide sensor based on a novel P

Author

Jin, Wang, Jian-Ming, Lei, Guo-Feng, Yang, Jun-Jun, Xue, Qing, Cai, Dun-Jun, Chen, Hai, Lu, Rong, Zhang, and You-Dou, Zheng

Abstract

The sensing properties of an α phase black phosphorus carbide (P2C2) monolayer for the adsorption of CO2, H2, H2O, N2, H2S, NH3, O2 and NO2 gases are theoretically investigated using first-principles calculations. We calculate the adsorption energy, equilibrium distance, Mulliken charge transfer, electron localization function, and work function to explore whether P2C2 is suitable for detecting NO2 gas. The results demonstrate that the P2C2 monolayer is highly sensitive and selective to NO2 gas molecules with robust adsorption energy and superior charge transfer due to the existence of strong orbital hybridization between the NO2 molecule and monolayer P2C2. In addition, the results of the work function calculations indicate that field effect transistor type NO2 gas sensors based on P2C2 monolayers are also feasible. Furthermore, the current-voltage curves reveal that the adsorption of NO2 can greatly modify the resistance of the P2C2 monolayer. Our results show that gas sensors based on P2C2 monolayers could be better than those based on black phosphorene (BP) for detecting NO2 molecules in an air mixture. In addition, the recovery time of the P2C2 sensor at T = 300 K was estimated to be short (and even shorter at higher temperatures) for NO2 which satisfies the demands for sustainable use.

Published
2018

9. Dielectric Properties of GaN in THz Frequencies

Author

He-Nan, Fang, primary, Rong, Zhang, additional, Bin, Liu, additional, Hai, Lu, additional, Jian-Ping, Ding, additional, Zi-Li, Xie, additional, Xiang-Qian, Xiu, additional, You-Dou, Zheng, additional, Ming-Wen, Xiao, additional, Cai-Hong, Zhang, additional, Jian, Chen, additional, and Pei-Heng, Wu, additional

Published
2010
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43. Theoretical optoelectronic analysis of intermediate-band photovoltaic material based on ZnY1−xOx (Y = S, Se, Te) semiconductors by first-principles calculations.

Author

Kong-Ping, Wu, Shu-Lin, Gu, Jian-Dong, Ye, Kun, Tang, Shun-Ming, Zhu, Meng-Ran, Zhou, You-Rui, Huang, Rong, Zhang, and You-Dou, Zheng

Subjects
OPTICAL properties, ELECTRONEGATIVITY, TERNARY alloys, DENSITY functional theory, SEMICONDUCTORS
Abstract

The structural, energetic, and electronic properties of lattice highly mismatched ZnY1−xOx (Y = S, Se, Te) ternary alloys with dilute O concentrations are calculated from first principles within the density functional theory. We demonstrate the formation of an isolated intermediate electronic band structure through diluted O-substitute in zinc-blende ZnY (Y = S, Se, Te) at octahedral sites in a semiconductor by the calculations of density of states (DOS), leading to a significant absorption below the band gap of the parent semiconductor and an enhancement of the optical absorption in the whole energy range of the solar spectrum. It is found that the intermediate band states should be described as a result of the coupling between impurity O 2p states with the conduction band states. Moreover, the intermediate bands (IBs) in ZnTeO show high stabilization with the change of O concentration resulting from the largest electronegativity difference between O and Te compared with in the other ZnSO and ZnSeO. [ABSTRACT FROM AUTHOR]

Published
2013
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44. The enhancement of light-emitting efficiency using GaN-based multiple quantum well light-emitting diodes with nanopillar arrays.

Author

Tu-Tu, Wan, Zhan-Qi, Ye, Tao, Tao, Zi-Li, Xie, Rong, Zhang, Bin, Liu, Xiang-Qian, Xiu, Yi, Li, Ping, Han, Yi, Shi, and You-Dou, Zheng

Subjects
ENERGY consumption, SEMICONDUCTORS, LIGHT emitting diodes, PHOTOLUMINESCENCE, SURFACE plasmons
Abstract

The quest for higher modulation speed and lower energy consumption has inevitably promoted the rapid development of semiconductor-based solid lighting devices in recent years. GaN-based light-emitting diodes (LEDs) have emerged as promising candidates for achieving high efficiency and high intensity, and have received increasing attention among many researchers in this field. In this paper, we use a self-assembled array-patterned mask to fabricate InGaN/GaN multi-quantum well (MQW) LEDs with the intention of enhancing the light-emitting efficiency. By utilizing inductively coupled plasma etching with a self-assembled Ni cluster as the mask, nanopillar arrays are formed on the surface of the InGaN/GaN MQWs. We then observe the structure of the nanopillars and find that the V-defects on the surface of the conventional structure and the negative effects of threading dislocation are effectively reduced. Simultaneously, we make a comparison of the photoluminescence (PL) spectrum between the conventional structure and the nanopillar arrays, achieved under an experimental set-up with an excitation wavelength of 325 mm. The analysis demonstrates that MQW-LEDs with nanopillar arrays achieve a PL intensity 2.7 times that of conventional LEDs. In response to the PL spectrum, some reasons are proposed for the enhancement in the light-emitting efficiency as follows: 1) the improvement in crystal quality, namely the reduction in V-defects; 2) the roughened surface effect on the expansion of the critical angle and the attenuated total reflection; and 3) the enhancement of the light-extraction efficiency due to forward scattering by surface plasmon polariton modes in Ni particles deposited above the p-type GaN layer at the top of the nanopillars. [ABSTRACT FROM AUTHOR]

Published
2013
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45. High Quantum Efficiency Back-Illuminated AlGaN-Based Solar-Blind Ultraviolet p-i-n Photodetectors.

Author

Guo-Sheng Wang, Hai Lu, Feng Xie, Dun-Jun Chen, Fang-Fang Ren, Rong Zhang, and You-Dou Zheng

Subjects
QUANTUM efficiency, ALUMINUM gallium nitride, PIN diodes, OPTOELECTRONIC devices, WAVELENGTHS, EPITAXY, THERMAL noise
Abstract

AlGaN-based back-illuminated solar-blind ultraviolet (UV) p-i-n photodetectors (PDs) with high quantum efficiency are fabricated on sapphire substrates. To improve the overall performance of the PD, a series of structural design considerations and growth procedures are implemented in the epitaxy process. A distinct wavelengthselective photo-response peak of the PD is obtained in the solar-blind region. When operating in photovoltaic mode, the PD exhibits a solar-blind/UV rejection ratio of up to 4 orders of magnitude and a peak responsivity of ∼113.5mA/W at 270 nm, which corresponds to an external quantum efficiency of ∼52%. Under a reverse bias of -5 V, the PD shows a low dark current of ∼1.8 pA and an enhanced peak quantum efficiency of ∼64%. The thermal noise limited detectivity is estimated to be ∼3.3 × 1013 cm·Hz1/2W-1. [ABSTRACT FROM AUTHOR]

Published
2012
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46. Design and Fabrication of AlGaN-Based Resonant-Cavity-Enhanced p-i-n UV PDs.

Author

Chao Nie, Ruo Lian Jiang, Xiao Li Ji, Zi Li Xie, Bin Liu, Ping Han, Rong Zhang, and You Dou Zheng

Subjects
ULTRAVIOLET radiation, OPTOELECTRONIC devices, SEMICONDUCTORS, CHEMICAL vapor deposition, ABSORPTION, REFRACTIVE index, SPECTRUM analysis, WAVELENGTHS, ELECTRONICS
Abstract

AIGaN-based resonant-cavity-enhanced (RCE) p-i-n photodetectors (PDs) for operating at the wavelength of 330 nm were designed and fabricated. A 20.5-pair AIN/Al0.3Ga0.7N distributed Bragg reflector (DBR) was used as the back mirror and a 3-pair AIN/AI0.3Ga0.7N DBR as the front one. In the cavity is a p--GaN/i-GaN/n-Al0.3Ga0.7N structure. The optical absorption of the RCE PD structure is at most 59.8% deduced from reflectance measurement. Selectively enhanced by the cavity effect, a response peak of 0.128 A/W at 330 nm with a half-peak breadth of 5.5 nm was obtained under zero bias. The peak wavelength shifted 15 nm with the incident angle of light increasing from 0° to 60°. [ABSTRACT FROM AUTHOR]

Published
2009
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49. Vacuum Violet Photo-Response of AlGaN-Based Metal-Semiconductor-Metal Photodetectors.

Author

Dong, Zhou, Hai, Lu, Dun-Jun, Chen, Fang-Fang, Ren, Rong, Zhang, You-Dou, Zheng, and Liang, Li

Subjects
PHOTODETECTORS, METAL-semiconductor-metal structures, ALUMINUM gallium nitride, FAR ultraviolet radiation, SYNCHROTRON radiation, BAND gaps, PHOTOEMISSION
Abstract

Al0.5Ga0.5 N-based metal-semiconductor-metal photodetectors (PDs) with a large device area of 5 × 5 mm2 are fabricated on a sapphire substrate, which are tested for vacuum ultraviolet light detection by using a synchrotron radiation source. The PD exhibits low dark current of less than 1 pA under 30 V bias and a spectral cutoff around 260 nm, corresponding to the energy bandgap of Al0.5Ga0.5N. A peak photo-responsivity of 14.68 mA/W at 250 nm with a rejection ratio (250/360 nm) of more than four orders of magnitude is obtained under 30 V bias. For wavelength less than 170 nm, the photoresponsivity of the PD is found to increase as wavelength decreases, which is likely caused by the enhanced photoemission effect. [ABSTRACT FROM AUTHOR]

Published
2013
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50. High Deep-Ultraviolet Quantum Efficiency GaN P-I-N Photodetectors with Thin P-GaN Contact Layer.

Author

Hai-Feng, LIAN, Guo-Sheng, WANG, LU Hai, Fang-Fang, REN, Dun-Jun, CHEN, Rong, ZHANG, and You-Dou, ZHENG

Subjects
OPTOELECTRONIC devices, QUANTUM efficiency, ULTRAVIOLET radiation, GALLIUM nitride, MICROFABRICATION, WAVELENGTHS
Abstract

GaN ultraviolet (UV) p-i-n photodetectors (PDs) with a 40nm thin p-GaN contact layer are fabricated on sapphire substrates, which exhibit enhanced quantum efficiency especially in a deep-UV wavelength range. The PDs show good rectification behavior and low dark current in pA level for reverse bias up to -10 V. Under zero bias, the maximum quantum efficiency of the PD at 360nm is close to 59.4% with a UV/visible rejection ratio more than 4 orders of magnitude. Even at a short wavelength of 280 nm, the quantum efficiency of the PD is still around 47.5%, which is considerably higher than that of a control device with a thicker p-GaN contact layer. The room temperature thermal noise limited detectivity of the PD is calculated to be ~4.96 × 1014 cm·Hz1/2W-1. [ABSTRACT FROM AUTHOR]

Published
2013
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