Hole Transport Manipulation To Improve the Hole Injection for Deep Ultraviolet Light-Emitting Diodes

Zhang, Zi Hui; Chen, Sung Wen Huang; Zhang, Yonghui; Li, Luping; Wang, Sheng Wen; Tian, Kangkai; Chu, Chunshuang; Fang, Mengqian; Kuo, Hao‐Chung; Bi, Wengang

doi:10.1021/acsphotonics.7b00443

Cited by 103 publications

(63 citation statements)

References 25 publications

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“…The equilibrium energy band diagram and the carrier distribution profiles (both electrons and holes) across the entire structure were simulated and analyzed using the commercially available software package Crosslight APSYS program. 48,49,50 The…”

Section: Methodsmentioning

confidence: 99%

Graded-Index Separate Confinement Heterostructure AlGaN Nanowires: Toward Ultraviolet Laser Diodes Implementation

Sun¹,

Priante²,

Min³

et al. 2018

ACS Photonics

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High-density dislocations in materials and poor electrical conductivity of p-type AlGaN layers constrain the performance of the ultraviolet light emitting diodes and lasers at shorter wavelengths. To address those technical challenges, we design, grow, and fabricate a novel nanowire structure adopting a graded-index separate confinement heterostructure (GRINSCH) in which the active region is sandwiched between two compositionally graded AlGaN layers, namely a GRINSCH diode. Calculated electronic band diagram and carrier concentrations show an automatic formation of a p-n junction with electron and hole concentrations of ~10 18 /cm 3 in the graded AlGaN layers without intentional doping. The transmission electron microscopy experiment confirms the composition variation in the axial direction of the graded AlGaN nanowires. Significantly lower turn-on voltage of 6.5 V (reduced by 2.5 V) and smaller series resistance of 16.7 Ω (reduced by nearly four times) are achieved in the GRINSCH diode, compared with the conventional p-in diode. Such an improvement in the electrical performance is mainly attributed to the effectiveness of polarization-induced nand p-doping in the compositionally graded AlGaN layers. In consequence, the carrier transport and injection efficiency of the GRINSCH diode are greatly enhanced, which leads to a lower turn-on voltage, smaller series resistance, higher output power, and enhanced device efficiency. The calculated carrier distributions (both

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Section: Methodsmentioning

confidence: 99%

Graded-Index Separate Confinement Heterostructure AlGaN Nanowires: Toward Ultraviolet Laser Diodes Implementation

Sun¹,

Priante²,

Min³

et al. 2018

ACS Photonics

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“…We perform numerical investigations by using APSYS. [ 24 ] The Auger recombination coefficient and the Shockley–Read–Hall (SRH) recombination lifetime are set to be 1.0 × 10 −30 cm 6 s −1 and 10 ns, respectively [ 25 ] The impact ionization coefficients are set to α n and α p for electrons and holes by Chynoweth's Equation () and (), respectively. [ 26 ] The critical electric field for GaN material is set to 3 MV cm −1 .…”

Section: Device Architectures and Parametersmentioning

confidence: 99%

Improving the Current‐Spreading Effect for GaN‐Based Quasi‐Vertical PIN Diode by Using an Embedded PN Junction

Liu

Jia

Zhang

et al. 2020

Physica Status Solidi (a)

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GaN‐based quasi‐vertical PIN diodes are grown on insulating sapphire substrates, and thus both the n‐electrode and the p‐electrode are made on the same side, which causes lateral current injection scheme. Therefore, one of the challenges for this design lies in the serious current crowding at the mesa edges, which leads to the local hole accumulation, and thus the Auger recombination significantly gives rise to the poor conductivity modulation in the drift region when the devices are forwardly biased. Herein, utilizing an embedded PN–GaN junction is proposed, such that the embedded PN–GaN junction is reversely biased when the PIN diode is in the on‐state condition. The built‐in electric field in the reversely biased PN–GaN junction depletes holes at the mesa edges, and correspondingly the Auger recombination can be decreased. The results also show that the proposed structures do not affect the breakdown voltage for PIN diodes.

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“…Ni (<3 nm)/Al and Pd (<10 nm)/Al hybrid metals exhibited reflectivities of ≈70% at 280 nm . However, despite these efforts, most of the metal schemes proposed for DUV LEDs have shown poor Ohmic contacts to p‐AlGaN; thereby, low hole injection efficiency . According to a theoretical simulation, the insertion of AlGaN interlayers provided an improved injection/transport of holes, while the use of a Ni/Al electrode could reduce the optical absorption .…”

Section: Introductionmentioning

confidence: 99%

Smart Wide‐Bandgap Omnidirectional Reflector as an Effective Hole‐Injection Electrode for Deep‐UV Light‐Emitting Diodes

Lee

Park

Shin

et al. 2019

Advanced Optical Materials

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Deep‐ultraviolet light‐emitting diodes (DUV‐LEDs) find widespread applications in various industries and are a focus area in environmental and life science research. However, the quantum efficiency of DUV‐LEDs is still low because of the unbalanced hole injection, high operation voltage, and low reflectivity of the p‐electrode. In this study, a smart wide‐bandgap omnidirectional reflector (ODR), which simultaneously acts as an effective hole‐injection electrode, is demonstrated for a flip‐chip DUV‐LED. The smart ODR is composed of p‐type AlGaN (p‐AlGaN)/Ni:AlN/Al with a high reflectivity of 94.2% at 280 nm, in which AlN with a theoretically calculated thickness of 40 nm is Ni‐doped using the pulsed electrical breakdown (PEBD) method. The smart ODR‐mounted AlGaN‐multiquantum‐well‐based DUV‐LED exhibits a remarkable wall‐plug efficiency (4.8%) and high external quantum efficiency (8.5%) at a low operation voltage of 9.75 V owing to the fused layer of Ni3N and Ga vacancies formed in the interfacial region of the p‐AlGaN and AlN layers, through the mutual diffusion of Ni and Ga during PEBD. The interface‐mediated Ohmic contact leads to an effective hole injection without reducing the reflectivity, yielding increased optical output and electric input powers. The proposed smart ODR can provide an innovative route for the manipulation of DUV light.

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Hole Transport Manipulation To Improve the Hole Injection for Deep Ultraviolet Light-Emitting Diodes

Cited by 103 publications

References 25 publications

Graded-Index Separate Confinement Heterostructure AlGaN Nanowires: Toward Ultraviolet Laser Diodes Implementation

Graded-Index Separate Confinement Heterostructure AlGaN Nanowires: Toward Ultraviolet Laser Diodes Implementation

Improving the Current‐Spreading Effect for GaN‐Based Quasi‐Vertical PIN Diode by Using an Embedded PN Junction

Smart Wide‐Bandgap Omnidirectional Reflector as an Effective Hole‐Injection Electrode for Deep‐UV Light‐Emitting Diodes

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