Low absorption loss p-AlGaN superlattice cladding layer for current-injection deep ultraviolet laser diodes

Martens, Martin; Kühn, Christian; Ziffer, Eviathar; Simoneit, Tino; Kueller, V.; Knauer, A.; Raß, Jens; Wernicke, Tim; Einfeldt, S.; Weyers, M.; Kneissl, Michael

doi:10.1063/1.4947102

Cited by 49 publications

(25 citation statements)

References 24 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%

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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%

III-Nitride Short Period Superlattices for Deep UV Light Emitters

Nikishin

2018

Applied Sciences

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“…In addition, a 2DEG is generated even when GaN is converted to AlGaN. The generation of a 2D hole gas has been confirmed in the AlGaN/AlN superlattice structure with the general + c ‐plane, and this technique led to the demonstration of a deep ultraviolet laser diode; the generation of a 2DEG using the N‐polar (Al)GaN/AlN structure was caused by the inverted structure toward the + c ‐plane.…”

Section: Simulation Of N‐polar Algan/gan Heterostructurementioning

confidence: 96%

Growth and Characterization of Nitrogen‐Polar AlGaN/AlN Heterostructure for High‐Electron‐Mobility Transistor

Ito

Sakamoto

Isono

et al. 2020

Physica Status Solidi (b)

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A nitrogen‐polar (N‐polar) AlGaN/AlN high‐electron‐mobility transistor (HEMT) is proposed, and the generation of a 2D electron gas (2DEG) is simulated. The band diagram of N‐polar (Al)GaN/AlN shows the generation of the 2DEG, whereas that of the conventional metal‐polar (Al)GaN/AlN structure shows the generation of a 2D hole gas. Furthermore, the concentration of the 2DEG is considerably high even when the (Al)GaN layer is as thin as a few nanometers. N‐polar AlGaN/AlN is grown on sapphire substrates with a misorientation angle of 2°; furthermore, atomic force microscope measurements in a range of 5 × 5 μm2 demonstrate that the root‐mean‐square value obtained from atomic force microscopy of N‐polar AlGaN is approximately 0.7 nm. N‐polar AlGaN layers with a thickness of approximately 40–60 nm with more than 50% Al content are almost coherently grown on the N‐polar AlN layer with a thickness of approximately 400 nm.

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“…A significant source of optical loss in DUV-LEDs is that of absorption in the highly absorbing p-side. Due to this there have been reports in the literature of low absorption alternatives [38,39,40]. In order to further understand the role of the NPSS in LEE, we combine the NPSS with two kinds of rear reflector.…”

Section: Introductionmentioning

confidence: 99%

Nanopatterned sapphire substrates in deep-UV LEDs: is there an optical benefit?

Manley¹,

Walde²,

Hagedorn³

et al. 2020

Opt. Express

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Light emitting diodes (LEDs) in the deep ultra-violet (DUV) offer new perspectives for multiple applications ranging from 3D printing to sterilization. However, insufficient light extraction severely limits their efficiency. Nanostructured sapphire substrates in aluminum nitride based LED devices have recently shown to improve crystal growth properties, while their impact on light extraction has not been fully verified. We present a model for understanding the impact of nanostructures on the light extraction capability of DUV-LEDs. The model assumes an isotropic light source in the semiconductor layer stack and combines rigorously computed scattering matrices with a multilayer solver. We find that the optical benefit of using a nanopatterned as opposed to a planar sapphire substrate to be negligible, if parasitic absorption in the p-side of the LED is dominant. If losses in the p-side are reduced to 20%, then for a wavelength of 265 nm an increase of light extraction efficiency from 7.8% to 25.0% is possible due to nanostructuring. We introduce a concept using a diffuse ('Lambertian') reflector as p-contact, further increasing the light extraction efficiency to 34.2%. The results underline that transparent p-sides and reflective p-contacts in DUV-LEDs are indispensable for enhanced light extraction regardless of the interface texture between semiconductor and sapphire substrate. The optical design guidelines presented in this study will accelerate the development of high-efficiency DUV-LEDs, but the model is also readily applicable to other multilayer opto-electronic nanostructured devices such as photovoltaics or photodetectors.

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Low absorption loss p-AlGaN superlattice cladding layer for current-injection deep ultraviolet laser diodes

Cited by 49 publications

References 24 publications

III-Nitride Short Period Superlattices for Deep UV Light Emitters

III-Nitride Short Period Superlattices for Deep UV Light Emitters

Growth and Characterization of Nitrogen‐Polar AlGaN/AlN Heterostructure for High‐Electron‐Mobility Transistor

Nanopatterned sapphire substrates in deep-UV LEDs: is there an optical benefit?

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