Efficient Carrier Confinement in Deep-Ultraviolet Light-Emitting Diodes With Composition-Graded Configuration

Chang, Jih‐Yuan; Chang, Ho‐Wan; Shih, Ya-Hsuan; Chen, Fang‐Ming; Huang, Man-Fang; Kuo, Yen−Kuang

doi:10.1109/ted.2017.2761404

Cited by 30 publications

(15 citation statements)

References 28 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%

“…Atomic-number sensitive (Z-contrast) STEM was realized by acquiring the data with high-angle annular dark-field (HAADF) detector. 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. − The energy band diagram of the structure was obtained by self-consistently solving Poisson’s equation under thermal equilibrium condition, meanwhile taking into account of the existence of strong spontaneous and piezoelectric polarization charges in the AlGaN alloys. For valence band, the 6 × 6 k · p method was adopted, taking into account the nonparabolic nature of the energy bands.…”

Section: Experimental Sectionmentioning

confidence: 99%

See 1 more Smart Citation

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%

Section: Experimental Sectionmentioning

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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show abstract

“…A direct method to suppress the electron leakage for DUV LEDs is to engineer the p‐EBL, for example, superlattice p‐EBL, p‐EBL with AlGaN insertion layer, p‐EBL with the graded AlN composition, superlattice last quantum barrier . Moreover, the electron concentration in the MQWs can be enhanced by proposing novel active region structure, for example, Si doped quantum barriers, grading the AlN composition for the AlGaN based quantum barriers, increasing the AlN composition for AlGaN based quantum barrier …”

Section: Enhance the Electron Injection Efficiency For Duv Ledsmentioning

confidence: 99%

Progress in External Quantum Efficiency for III‐Nitride Based Deep Ultraviolet Light‐Emitting Diodes

Chu

Tian

Zhang

et al. 2019

Physica Status Solidi (a)

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AlGaN-based deep ultraviolet light-emitting diodes (DUV LEDs) are featured with small size, DC driving, no environmental contamination etc., and they are now emerging as the excellent solid-state light source to replace the conventional mercury based light tubes. Nevertheless, the DUV LEDs are currently affected by the poor external quantum efficiency (EQE), which is caused by the low internal quantum efficiency (IQE) and the very unsatisfying light extraction efficiency (LEE). In this work, the authors disclose the underlying mechanism for the low EQE and summarize the technologies that have been adopted so far for enhancing the EQE.

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“…It is well known that the polarization-induced electric field between the last quantum barrier layer (LQB) in MQWs and the p-type layer lowers the energy band at the interface, causing electrons to leak into the p-type, thereby participating in non-radiative recombination [10]. Various approaches, such as employing high Al composition AlGaN electron blocking layer (EBL) [11], graded EBL [12], insertion layer in EBL [13], and multi-quantum barriers EBL [14], have been put forward to cope with this problem. Besides, lowering the dislocation density is as well considered a working way to maximize luminous efficiency.…”

Section: Introductionmentioning

confidence: 99%

Enhancing the Luminous Efficiency of Ultraviolet Light Emitting Diodes By Adjusting the Al Composition of Pre-Well Superlattice

Wang

Jiang

et al. 2021

IEEE Photonics J.

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The lower luminous efficiency is a critical issue for ultraviolet light-emitting diodes (UV-LEDs) owing to the poor carrier injection efficiency and high dislocation density. Here, we can improve the luminous efficiency in two avenues by adjusting the Al composition of the InGaN/AlxGa1-xN pre-well superlattice. First, due to the strain-induced piezoelectric and intrinsic spontaneous polarization, a large number of electrons gather at the InGaN/AlxGa1-xN interface, which improves the electron concentration of the pre-well superlattice and lowers the conduction band energy of the first quantum barrier layer (FQB), thus enhancing the electron injection efficiency. Second, the pre-well superlattice can act as a hole blocking layer to prevent holes from leaking into the n-type layer and confine them in the quantum well layer. As the Al composition increases, the hole blocking effect of the pre-well superlattice is strengthened. However, higher Al composition decreases the lattice quality, which makes it possible for carrier loss through defect-related non-radiative recombination. Finally, the output power of the samples with 5% Al composition in the pre-well superlattice is 5.9% and 102.5% higher than that of the samples with 3% and 7% Al composition, respectively.

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Efficient Carrier Confinement in Deep-Ultraviolet Light-Emitting Diodes With Composition-Graded Configuration

Cited by 30 publications

References 28 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

Progress in External Quantum Efficiency for III‐Nitride Based Deep Ultraviolet Light‐Emitting Diodes

Enhancing the Luminous Efficiency of Ultraviolet Light Emitting Diodes By Adjusting the Al Composition of Pre-Well Superlattice

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