Double-side step-graded AlGaN electron blocking layer for nearly droop-free GaN-based blue LEDs

Prasad, S.; Mondal, Ramit Kumar; Chatterjee, Vijay; Pal, Saurabh

doi:10.1016/j.spmi.2019.106167

Cited by 7 publications

(3 citation statements)

References 31 publications

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“…For example, the application of an EBL composed of three thin p-type AlxGa1−xN layers with step-graded values of x = 0.04, 0.08, and 0.12 was found to limit the observed droop in the EQE to just 29% less than its initial value, while the application of a 50 nm thick p-type Al0.16Ga0.84N EBL exhibited a corresponding decrease of 44% [11]. In addition, the application of double-sided, step-graded AlxGa1−xN EBL, with x being 5%, 10%, and 15% and a step width of 4 nm along each growth direction (from the last QW to p-AlGaN), improves internal quantum efficiency (IQE), optical output power, and nearly eliminating the droop in the IQE [12]. While these past studies have demonstrated the beneficial impact of step-graded AlxGa1−xN EBLs on the IQE droop of GaN-based LEDs, absolute enhancements in the IQE and optical output power of the devices remain limited because hole injection is affected by the downward band-bending induced by the serious polarization at the interface between the EBL and the last QB of the LED [13,14].…”

Section: Introductionmentioning

confidence: 99%

Improved Performance of GaN-Based Ultraviolet LEDs With Electron Blocking Layers Composed of Double-Peak p-Type Al_xGa_1−xN/GaN Superlattice Layers

2021

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Past studies have demonstrated the positive impact of step-graded p-type AlxGa1−xN/GaN superlattice (SL) electron blocking layer (EBL) structures on the efficiency performance of ultraviolet (UV) GaN-based light-emitting diodes (LEDs). However, the optimal Al-grading structure of these SL EBLs remains unclear owing to a lack of systematic investigation. The present work addresses this issue by applying EBL composed of alternating half-peak, single-peak, and double-peak p-type AlxGa1−xN/GaN SL structures with varying values of x ranging from 0.05 to 0.15 in 0.05 step increments. Simulation analysis is employed to obtain the internal quantum efficiency (IQE), energy band diagrams, polarization compensation factor, hole concentration, and electron concentration of GaN-based UV LEDs with three different SL-EBL structures. The results obtained at an injection current of 200 mA demonstrate that UV LEDs with double-peak SL-EBL structures provide the maximum IQE, which is ~38% greater than that of devices employing the conventional EBL in simulation experiment. This SL-EBL is demonstrated to improve the hole injection and electron overflow performance of GaN-based UV LEDs owing to the polarization charge and lattice mismatch at the p-AlxGa1−xN/GaN interfaces. The reduced Al composition on the p-GaN side reduces the potential barrier of hole injection. Moreover, the predicted increase in the IQE of GaN-based UV LEDs with the optimal SL-EBL is verified experimentally.

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Section: Introductionmentioning

confidence: 99%

Improved Performance of GaN-Based Ultraviolet LEDs With Electron Blocking Layers Composed of Double-Peak p-Type Al_xGa_1−xN/GaN Superlattice Layers

2021

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“…A number of bandgap engineering schemes [10], including modulated superlattice electron blocking layer (EBL) [11], varied superlattice EBL [12], N-face superlattice EBL [13], step-superlattice EBL [14], single side linear graded and step graded EBL [15,16], AlInGaN/AlInGaN superlattice EBL [17], ultrathin AlGaN/ InAlN heterojunction EBL [18], saw tooth EBL [19], AlN inserted layer [20] have been employed focusing performance improvements of DUV LED. Researchers have reported double side graded EBL structures for InGaN based LEDs [21,22]. However, detailed device physics along with career transport mechanism for this kind of structures yet to be properly explained.…”

Section: Introductionmentioning

confidence: 99%

Suppression of efficiency droop in AlGaN based deep UV LEDs using double side graded electron blocking layer

Mondal

Chatterjee

Prasad

et al. 2020

Semicond. Sci. Technol.

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We have envisaged and designed a novel III-V nitride based deep ultraviolet light emitting diode (LED) with reasonably high efficiency at higher current density using a double-side grading in electron blocking layer (EBL). Double-side step-and linear-grading in EBL yield better performance attributable to improved hole injection, stifled electron overflow and diminished electrostatic field in the active region. The performance curves indicate that double sided linear grading in EBL has 5.63 times enhancement in power compared to the conventional LED and the efficiency droop is as low as 15% at the current density of 200 A cm −2 for the emission wavelength of ∼273 nm.

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“…15 To resolve the aforementioned problems, numerous strategies have been published such as compositional grading of QWs for the reduction of piezoelectric field, compositional grading of quantum barriers (QBs) for the improvement of carrier transport, and grading electron blocking layer (EBL) for enhanced hole injection. [16][17][18] Quaternary (AlInGaN) and ternary (AlInN/GaN) EBLs have also been reported for better confinement of carriers within the active region. 19,20 Similarly, linearly graded (in the growth direction) AlGaN EBL has also been reported for efficient enhancement in comparison to conventional AlGaN EBL (with a fixed composition of Al: 20%).…”

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confidence: 99%

Review—A Survey of Simulations on Device Engineering of GaN-Based Light-Emitting Diodes

Usman

Anwar

Munsif

2020

ECS J. Solid State Sci. Technol.

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In InGaN-based light-emitting diodes, efficiency droop at high current density degrades device performance. Different strategies have been proposed by researchers to enhance the performance of InGaN-based light-emitting diodes numerically. We present a survey of the notable reported efficient simulated device structures, to date. We also discuss the simulation methodology employed in the state-of-the-art numerical simulators to study InGaN-based light-emitting diodes. Our survey gathers the influence of the layer engineering of each layer on the device performance of light-emitting diodes. Thus, different reported structures address the efficiency droop problem differently, thus, showing better optoelectronic properties as compared to the conventional structure.

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Double-side step-graded AlGaN electron blocking layer for nearly droop-free GaN-based blue LEDs

Cited by 7 publications

References 31 publications

Improved Performance of GaN-Based Ultraviolet LEDs With Electron Blocking Layers Composed of Double-Peak p-Type Al_xGa_1−xN/GaN Superlattice Layers

Improved Performance of GaN-Based Ultraviolet LEDs With Electron Blocking Layers Composed of Double-Peak p-Type Al_xGa_1−xN/GaN Superlattice Layers

Suppression of efficiency droop in AlGaN based deep UV LEDs using double side graded electron blocking layer

Review—A Survey of Simulations on Device Engineering of GaN-Based Light-Emitting Diodes

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Double-side step-graded AlGaN electron blocking layer for nearly droop-free GaN-based blue LEDs

Cited by 7 publications

References 31 publications

Improved Performance of GaN-Based Ultraviolet LEDs With Electron Blocking Layers Composed of Double-Peak p-Type Al x Ga1−x N/GaN Superlattice Layers

Improved Performance of GaN-Based Ultraviolet LEDs With Electron Blocking Layers Composed of Double-Peak p-Type Al x Ga1−x N/GaN Superlattice Layers

Suppression of efficiency droop in AlGaN based deep UV LEDs using double side graded electron blocking layer

Review—A Survey of Simulations on Device Engineering of GaN-Based Light-Emitting Diodes

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Product

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Improved Performance of GaN-Based Ultraviolet LEDs With Electron Blocking Layers Composed of Double-Peak p-Type Al_xGa_1−xN/GaN Superlattice Layers

Improved Performance of GaN-Based Ultraviolet LEDs With Electron Blocking Layers Composed of Double-Peak p-Type Al_xGa_1−xN/GaN Superlattice Layers