Short period p-type AlN/AlGaN superlattices for deep UV light emitters

Nikishin, S. A.; Borisov, B.; Мансуров, В. Г.; Pandikunta, Mahesh; Chary, I.; Rajanna, Gautam; Bernussi, A. A.; Kudriavtsev, Yuriy; Asomoza, R.; Bulashevich, K. A.; Karpov, S. Yu.; Sohal, Sandeep; Holtz, M.

doi:10.1557/proc-1202-i10-03

Cited by 5 publications

(9 citation statements)

References 9 publications

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“…It is clearly seen that the hole concentration varies very little with the temperature in SPSLs, and is highly dependent on the temperature (almost 1.5 orders of magnitude) in a uniformly Mg-doped Al 0.05 Ga 0.95 N layer. Similar experimental results were reported by many different teams [45,[105][106][107][108][109][110][111][112][113][114][115].…”

Section: Aln/alga(in)n Spsl Doping and Ohmic Contactssupporting

confidence: 88%

“…The concentration of holes can be at the level of 10 18 cm −3 , even in SPSLs with high average AlN content, as is seen in Figure 6a. Such structures were obtained using both MBE and MOCVD methods [25,41,42,45,91,[105][106][107][108][109][110]. Figure 6b shows the results of temperature-dependent Hall characterization of three SPSLs and one AlGaN layer.…”

Section: Aln/alga(in)n Spsl Doping and Ohmic Contactsmentioning

confidence: 99%

“…One could conclude that the efficiency of Mg activation is a very weak function of temperature in wide bandgap AlN/Al x Ga 1−x (In)N SPSL (E g from~4.2 to~5.3 eV) [107,108]. Thus, these SPSLs are very attractive for fabrication of transparent low resistive ohmic contacts for deep UV light emitters.…”

Section: Appl Sci 2018 8 X For Peer Reviewmentioning

confidence: 99%

“…Similar approach was successfully used for fabrication of ohmic contacts on p-type AlN/Al x Ga 1−x N SPSLs [108]. obtained by self-consistent solution of the Poisson and Schrödinger equations [76], accounting for the complex valence band structure of III-nitrides [116].…”

Section: Appl Sci 2018 8 X For Peer Reviewmentioning

confidence: 99%

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III-Nitride Short Period Superlattices for Deep UV Light Emitters

Nikishin

2018

Applied Sciences

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III-Nitride short period superlattices (SPSLs), whose period does not exceed ~2 nm (~8 monolayers), have a few unique properties allowing engineering of light-emitting devices emitting in deep UV range of wavelengths with significant reduction of dislocation density in the active layer. Such SPSLs can be grown using both molecular beam epitaxy and metal organic chemical vapor deposition approaches. Of the two growth methods, the former is discussed in more detail in this review. The electrical and optical properties of such SPSLs, as well as the design and fabrication of deep UV light-emitting devices based on these materials, are described and discussed.

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Section: Aln/alga(in)n Spsl Doping and Ohmic Contactssupporting

confidence: 88%

Section: Aln/alga(in)n Spsl Doping and Ohmic Contactsmentioning

confidence: 99%

Section: Appl Sci 2018 8 X For Peer Reviewmentioning

confidence: 99%

Section: Appl Sci 2018 8 X For Peer Reviewmentioning

confidence: 99%

See 2 more Smart Citations

III-Nitride Short Period Superlattices for Deep UV Light Emitters

Nikishin

2018

Applied Sciences

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“…Thus, various methods have been developed, including p-GaN contact layer [117][118][119][120] and superlattice structures, 38,[121][122][123][124][125][126][127][128][129][130] in order to achieve efficient current injection into Al-rich p-Al x Ga 1-x N.…”

Section: 99mentioning

confidence: 99%

Review—Group III-Nitride-Based Ultraviolet Light-Emitting Diodes: Ways of Increasing External Quantum Efficiency

Park

Kim

Cho

et al. 2017

ECS J. Solid State Sci. Technol.

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There is a rapidly growing demand for highly efficient ultraviolet (UV) light sources for a wide variety of applications. In particular, state-of-the-art AlGaN deep UV light-emitting diodes (DUV LEDs) exhibit inadequately low external quantum efficiencies (EQEs). The low efficiencies are attributed to the inherent material properties of high-Al-content AlGaN including strained epitaxial layers, low carrier concentrations, and strong transverse magnetic (TM)-polarized light emission. Extensive efforts have been made to tackle these challenging issues and technological developments have been achieved and enabled the fabrication of reasonable EQE LEDs. In this review, recent advances in the growth of high-quality AlGaN epitaxial layers, transparent and reflective ohmic contacts, and light extraction for AlGaN-based UV LEDs are reviewed. Al x Ga 1-x N-based ultraviolet light-emitting diodes (UV LEDs) are of technological importance because of their applications in numerous areas such as water purification, biological analysis, sensing, epoxy curing, high-density optical storage, white light illumination, UV adhesives, 3-dimensional (3D) printer and UV-coating.1,2 These applications are made possible because of their wide bandgap energy range in the UV spectrum, which spans from 6.2 eV (AlN) to 3.4 eV (GaN), namely, from UV-A (320-400 nm), UV-B (290-320 nm) to UV-C (200-290 nm).3-7 The external quantum efficiency (EQE) of Al x Ga 1-x N-based UV LEDs decreases rapidly as the molar fraction (x) of Al increases, namely, as the wavelength decreases, as illustrated in Figure 1. 8 Thus, a great deal of effort has been made in order to improve the EQE of UV LEDs. The effort notwithstanding, however, the EQE of AlGaN-based UV LEDs is still insufficiently low. The typical EQE of UV LEDs, specifically in the UV-C spectral range (100-280 nm), is less than 5% and decreases down to 10 -6 % for 210-nm AlN-based UV LEDs. 4 These low EQEs are associated with the intrinsic material properties of Al x Ga 1-x N.1,2 Figure 2 exhibits a schematic diagram of a typical AlGaN UV LED structure grown on a sapphire substrate. The structure consists of a Si-doped n-type AlGaN, an Al x Ga 1-x N/Al y Ga 1-y N multiple-quantum well (MQW) active region, an AlGaN-based electron-blocking layer (EBL), a Mg-doped p-type AlGaN, and a Mg-doped p-type GaN. Almost every layer in the structure poses different technical issues, which limit the efficiency of UV LEDs, as shown in Figure 2. First, increasing the Al content generally results in a poor crystallinity of AlGaN epilayers, causing a poor internal quantum efficiency (IQE). Second, both n-type and ptype doping efficiencies of AlGaN are difficult to increase because the ionization energies of acceptor (Mg) and donor (Si) dopants largely increase with increasing Al content. The low doping efficiency causes several technological problems: (i) a poor electrical efficiency (EE) attributable to high-resistance contacts on resistive n-type and p-type AlGaN; (ii) current crowding causing non-uniform current in...

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High performance and high yield sub-240 nm AlN:GaN short period superlattice LEDs grown by MBE on 6 in. sapphire substrates

Nicholls,

Anderson,

Lee

et al. 2023

Applied Physics Letters

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We develop ultraviolet (UV) light emitting diodes (LEDs) that operate in the sub-240 nm (far UVC) regime. The traditional limitations of high Al content AlGaN—the low light extraction efficiency due to transverse magnetic polarization and the poor doping efficiency—were overcome by using AlN:GaN short period superlattices (SPSLs) of varying compositions throughout almost the entire device structure. The quality of our molecular beam epitaxy process for growing SPSL devices was verified via transmission electron microscopy and x-ray diffraction—together, these demonstrate our capacity for growing high quality interfaces with a great deal of control over the thicknesses of each individual layer. Resistivity measurements of our SPSL were three times smaller than bulk AlGaN of similar composition due to the improved doping efficiency. Devices fabricated on 6 in. sapphire substrates showed uniform performance, leading to over 10 000 functional devices per wafer. Packaged diodes exhibited a peak wall plug efficiency of 0.55% and an output power of 1.7 mW when operated at peak efficiency. The devices had an operating life (70% initial power) of 2800 h (at 20 mA continuous wave). Additionally, they could be driven as high as 1 A, which resulted in a record for radiant flux of a far UVC LED grown on sapphire (17.4 mW).

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Short period p-type AlN/AlGaN superlattices for deep UV light emitters

Cited by 5 publications

References 9 publications

III-Nitride Short Period Superlattices for Deep UV Light Emitters

III-Nitride Short Period Superlattices for Deep UV Light Emitters

Review—Group III-Nitride-Based Ultraviolet Light-Emitting Diodes: Ways of Increasing External Quantum Efficiency

High performance and high yield sub-240 nm AlN:GaN short period superlattice LEDs grown by MBE on 6 in. sapphire substrates

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