Anisotropy and Mechanistic Elucidation of Wet‐Chemical Gallium Nitride Etching at the Atomic Level

Tautz, Markus; Weimar, A.; Graßl, Christian; Welzel, Martin; Díaz, David Díaz

doi:10.1002/pssa.202000221

Cited by 12 publications

(25 citation statements)

References 37 publications

(57 reference statements)

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“…This has led to an opportunity for hydroxide ions to reach Ga atoms in defect-rich areas progressing the wet etching process. 42,43 More detailed explanation and characteristics of this hybrid etching method combining both ICP-RIE and KOHbased wet etching processes on different stacks of GaN layers have been described in our former studies and the reports from other groups. 42−46 We have also demonstrated to employ this hybrid etching technique for realizing both field-effect transistors and LEDs based on vertical GaN nanowire arrays.…”

Section: Methodsmentioning

confidence: 97%

“…Afterward, the sample was subsequently treated in a potassium hydroxide (KOH)-based wet chemical etchant to smoothen the GaN surface at a temperature of 80 °C for 20 min. From other reported studies using hydroxide ions (OH – ) as an active etchant, it was found that Ga- and N-polar GaN materials possess different etching behaviors. − As a key prerequisite for anisotropic KOH etching to occur on GaN, the hydroxide ions have to be able to access the Ga atom for the oxidation process. Thus, hexagonal pyramids can be formed when N-polar GaN areas were exposed to KOH solution .…”

Section: Methodsmentioning

confidence: 99%

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Ultrashort Pulse Laser Lift-Off Processing of InGaN/GaN Light-Emitting Diode Chips

Yulianto

Kadja

Bornemann

et al. 2021

ACS Appl. Electron. Mater.

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Gallium nitride (GaN) film delamination is an important process during the fabrication of GaN light-emitting diodes (LEDs) and laser diodes. Here, we utilize 520 nm femtosecond laser pulses, exploiting nonlinear absorption rather than single-photon absorption such as in conventional laser lift-off (LLO) employing excimer or Q-switched laser sources. The focus of this study is to investigate the influence of laser scanning speed and integrated fluence corresponding to laser energy per area during the LLO processing of GaN LED chips and their resulting structural properties. Because both the sapphire substrate and InGaN/GaN heterostructures are fully transparent to the emission of the laser system, a key question is related to the impact of laser pulses on the quality of a thin film structure. Therefore, several characterization methods (i.e., scanning electron microscopy, atomic force microscopy, X-ray diffraction, Raman spectroscopy, and electroluminescence spectroscopy) were employed to understand the material modifications made by femtosecond LLO (fs-LLO). We demonstrated that by adjusting the laser scanning speed, smooth GaN surfaces and good crystal quality could be obtained regardless of the existing delamination of metal contact, which then slightly downgraded the LED performance. Here, the integrated fluence level was set in the range of 2.6–4.4 J/cm2 to enable the fs-LLO process. Moreover, two mitigation strategies were developed and proven to improve the optoelectrical characteristics of the lifted-off LEDs (i.e., modification of the processing step related to the metal creation and reduction of laser energy).

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Section: Methodsmentioning

confidence: 97%

Section: Methodsmentioning

confidence: 99%

Ultrashort Pulse Laser Lift-Off Processing of InGaN/GaN Light-Emitting Diode Chips

Yulianto

Kadja

Bornemann

et al. 2021

ACS Appl. Electron. Mater.

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“…where I x and I sub are the peak intensities of the species and substrate, respectively, l sub is the effective attenuation length for quantitative analysis (NIST database), and N sub is the atomic concentration (Ga + N) in the substrate (at cm −3 ). 36 22,[26][27][28]32 A typical etch rate for a 1 M KOH solution at 80 °C is 25 nm/min. 33 The dissolution reaction is described using eq 1 22, 30,31 GaN 3H O OH Ga(OH) NH…”

Section: Methodsmentioning

confidence: 99%

“…26,29−32 It is surprising that relatively little attention has been paid to the basic chemistry involved in the uniform etching process. 23,30,32 This will be the main topic in the first part of the paper (Section 3.1). In a previous study by Weyher et al 33 it was shown that, after brief photogalvanic etching, subsequent chemical etching of the Ga-polar surface was possible.…”

Section: Introductionmentioning

confidence: 99%

Chemical Etching of GaN in KOH Solution: Role of Surface Polarity and Prior Photoetching

et al. 2022

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Surface polarity plays a significant role in chemical etching of GaN in KOH solution, a process that is important for quality control and device fabrication. In this work, basic chemical mechanisms are proposed to explain the role of surface orientation in the chemical etching of the semiconductor. In addition, it is shown how prior photoetching of inert surfaces [the polar (0001), semipolar (101̅ 1̅ ), and nonpolar (11̅ 00) interfaces] enables chemical etching. Photoetching gives rise to the formation of nanocolumns on dislocations and to protrusions on nanoscale inhomogeneities. Subsequent etching in KOH solution leads to the development of distinctive features that depend on the crystal orientation of the surface and the presence of the inhomogeneities. The morphology of the photoetched surfaces was revealed by scanning electron microscopy, while X-ray photoelectron spectroscopy measurements were used to investigate the surface chemistry of these processes.

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“…Figure12. The surface was covered (for simplicity) with a 300 nm-thick carbon layer, which was patterned by FIB (dark spots in the image).…”

mentioning

confidence: 99%

Pyramid Formation by Etching of InxGa1−xN/GaN Quantum Well Structures Grown on N‐face GaN for Nanooptical Light Emitters

Rossów

Sidikejiang

Hagag

et al. 2021

Physica Status Solidi (b)

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Nanooptical light emitters based on semiconductors are very promising for a broad range of applications such as single-photon sources or optical sensors of nanoobjects. The group-III nitrides are especially interesting in this respect as light emitters in the visible range with high efficiency are nowadays commercially available. By changing the indium content, the bandgap of In x Ga 1Àx N can in principle be tuned over the whole wavelength range from the near-IR region to the near-UV region. In most studies, three routes are followed to produce nanooptical light emitters: 1) the self-assembled growth of quantum dots (QDs), [1,2] 2) the growth of pyramids by applying masks of, for example, SiO 2 , [3] or 3) the growth [4,5] or topÀdown fabrication [6] of nanorods. The first one suffers from the high defect density in group-III nitride growth when using conventional sapphire, SiC, or silicon substrates, [7] that the sites of the QDs are unknown (unless further steps are taken), the properties are critically dependent on the growth conditions, and that it is difficult to stabilize the QDs in further growth. The second one has the problem that indium incorporation on different parts of the pyramid, side facets, edges, and tip, varies and is difficult to control, which typically result in an inhomogeneous emission. Furthermore, defects may form, induced by the mask, which reduce the efficiency. The insertion of QDs in nanorods during growth shows, up to now, low efficiency. A topÀdown approach to realize QDs in etched nanorods would be quite a challenge due to the length of the nanorods and the small required diameters.Hence, for the generation of a large array of as similar as possible nanooptical light emitters, we propose another solution. A single or multiquantum well (SQW, MQW) structure is grown on N-face GaN and in a second step pyramids are formed by wet chemical etching. This has the advantage that the QW can be optimized independently of pyramid formation. However, in contrast to the N face, the Ga face is chemically inert and plasma etching processes may create damage, which reduces the efficiency. Another advantage of using N-face GaN is that the

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Anisotropy and Mechanistic Elucidation of Wet‐Chemical Gallium Nitride Etching at the Atomic Level

Cited by 12 publications

References 37 publications

Ultrashort Pulse Laser Lift-Off Processing of InGaN/GaN Light-Emitting Diode Chips

Ultrashort Pulse Laser Lift-Off Processing of InGaN/GaN Light-Emitting Diode Chips

Chemical Etching of GaN in KOH Solution: Role of Surface Polarity and Prior Photoetching

Pyramid Formation by Etching of InxGa1−xN/GaN Quantum Well Structures Grown on N‐face GaN for Nanooptical Light Emitters

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