Improved performance of GaN based light emitting diodes with ex-situ sputtered AlN nucleation layers

Chen, Shuo Wei; Li, Heng; Lu, Tien−Chang

doi:10.1063/1.4947299

Cited by 20 publications

(21 citation statements)

References 25 publications

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“…The cross-sectional SEM images of GaN films on 10, 25, and 40 nm sputtered AlON/PSS templates were taken from the [ 11 , 12 , 13 , 14 , 15 , 16 , 17 , 18 , 19 , 20 ] direction, presented in Figure 5 . From the cross-sectional SEM image of the GaN film on the 10 nm sputtered AlON/PSS template, we could clearly observe that GaN could not coalesce well.…”

Section: Resultsmentioning

confidence: 99%

“…Compared to MOCVD-grown AlN or GaN NLs, Li-Chuan Chang et al found that the utilization of ex situ sputtered AlN NLs could suppress GaN nucleation on cones and improve the quality of GaN films on PSSs [ 17 ]. Subsequently, many works proved that the utilization of sputtered AlN/PSS templates could improve the performance of GaN-based LEDs [ 18 , 19 ]. However, small GaN crystals on the cones’ surface of sputtered AlN/PSS templates may still deteriorate the crystal quality [ 15 , 20 , 21 ].…”

Section: Introductionmentioning

confidence: 99%

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Comparative Research of GaN Growth Mechanisms on Patterned Sapphire Substrates with Sputtered AlON Nucleation Layers

Gao

Peng

et al. 2020

Materials

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The utilization of sputtered AlN nucleation layers (NLs) and patterned sapphire substrates (PSSs) could greatly improve GaN crystal quality. However, the growth mechanism of GaN on PSSs with sputtered AlN NLs has not been thoroughly understood. In this paper, we deposited AlON by sputtering AlN with O2, and we found that the variation of thickness of sputtered AlON NLs greatly influenced GaN growth on PSSs. (1) For 10 nm thin AlON sputtering, no AlON was detected on the cone sidewalls. Still, GaN nucleated preferably in non-(0001) orientation on these sidewalls. (2) If the thickness of the sputtered AlON NL was 25 nm, AlON formed on the cone sidewalls and flat regions, and some small GaN crystals formed near the bottom of the cones. (3) If the sputtered AlON was 40 nm, the migration ability of Ga atoms would be enhanced, and GaN nucleated at the top of the cones, which have more chances to grow and generate more dislocations. Finally, the GaN growth mechanisms on PSSs with sputtered AlON NLs of different thicknesses were proposed.

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Comparative Research of GaN Growth Mechanisms on Patterned Sapphire Substrates with Sputtered AlON Nucleation Layers

Gao

Peng

et al. 2020

Materials

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“…Therefore, it can be clearly seen that the formation of V-shaped pits and dislocation distribution can be traced back to the cone tips of PSS. The accumulation of dislocation can form the V-pits and lead to the relaxation of compressive strain above the cone area of PSS30.…”

Section: Resultsmentioning

confidence: 99%

Three dimensional characterization of GaN-based light emitting diode grown on patterned sapphire substrate by confocal Raman and photoluminescence spectromicroscopy

Cheng

Chen

et al. 2017

Sci Rep

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We performed depth-resolved PL and Raman spectral mappings of a GaN-based LED structure grown on a patterned sapphire substrate (PSS). Our results showed that the Raman mapping in the PSS-GaN heterointerface and the PL mapping in the InxGa1−xN/GaN MQWs active layer are spatially correlated. Based on the 3D construction of E2(high) Raman peak intensity and frequency shift, V-shaped pits in the MQWs can be traced down to the dislocations originated in the cone tip area of PSS. Detail analysis of the PL peak distribution further revealed that the indium composition in the MQWs is related to the residual strain propagating from the PSS-GaN heterointerface toward the LED surface. Numerical simulation based on the indium composition distribution also led to a radiative recombination rate distribution that shows agreement with the experimental PL intensity distribution in the InxGa1−xN/GaN MQWs active layer.

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“…The LED structure comprised a PSS (cone shape pattern with pitch = 3.0 µm, pattern diameter = 2.8 µm, and pattern height = 1.8 µm) with an ex situ 25-nm-thick AlN nucleation layer deposited through physical vapor deposition. The ex-situ AlN layer can provide a more satisfactory crystal quality in the subsequent thick GaN layer in the first step of LED growth than a traditional GaN buffer layer at a low temperature can [35]. After the buffer layer, a 3-µm-thick unintentionally doped GaN layer (u-GaN) was incorporated into GaN-based LED structures, and then, for preparing samples A/D, B/E, and C/F, 2-, 4-, and 6-µm-thick n-GaN layers (n-doping concentration = 2 × 10 19 cm −3 ) were introduced in GaN-based LED structures, respectively.…”

Section: Methodsmentioning

confidence: 99%

Effect of Strains and V-Shaped Pit Structures on the Performance of GaN-Based Light-Emitting Diodes

Chen

2020

Crystals

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Strains and V-shaped pits are essential factors for determining the efficiency of GaN-based light-emitting diodes (LEDs). In this study, we systematically analyzed GaN LED structures on patterned sapphire substrates (PSSs) with two types of growth temperature employed for prestrained layers and three different thickness of n-type GaN layers by using cathodoluminescence (CL), microphotoluminescence (PL), and depth-resolved confocal Raman spectroscopy. The results indicated that V-pits formation situation can be analyzed using CL. From the emission peak intensity ratio of prestrained layers and multiple quantum wells (MQWs) in the CL spectrum, information regarding strain relaxation between prestrained layers and MQWs was determined. Furthermore, micro-PL and depth-resolved confocal Raman spectroscopy were employed to validate the results obtained from CL measurements. The growth conditions of prestrained layers played a dominant role in the determination of LED performance. The benefit of the thick layer of n-GaN was the strain reduction, which was counteracted by an increase in light absorption in thick n-type doped layers. Consequently, the most satisfactory LED performance was observed in a structure with relatively lower growth temperature of prestrained layers that exhibited larger V-pits, leading to higher strain relaxation and thinner n-type GaN layers, which prevent light absorption caused by n-type GaN layers.

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Improved performance of GaN based light emitting diodes with ex-situ sputtered AlN nucleation layers

Abstract: ARTICLES YOU MAY BE INTERESTED INHigh-quality and highly-transparent AlN template on annealed sputter-deposited AlN buffer layer for deep ultra-violet light-emitting diodes AIP Advances 7, 055110 (2017)

Cited by 20 publications

References 25 publications

Comparative Research of GaN Growth Mechanisms on Patterned Sapphire Substrates with Sputtered AlON Nucleation Layers

Comparative Research of GaN Growth Mechanisms on Patterned Sapphire Substrates with Sputtered AlON Nucleation Layers

Three dimensional characterization of GaN-based light emitting diode grown on patterned sapphire substrate by confocal Raman and photoluminescence spectromicroscopy

Effect of Strains and V-Shaped Pit Structures on the Performance of GaN-Based Light-Emitting Diodes

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