Straight and Smooth Etching of GaN (1100) Plane by Combination of Reactive Ion Etching and KOH Wet Etching Techniques

Itoh, Morimichi; Kinoshita, Toru; Koike, Choshiro; Takeuchi, Misaichi; Kawasaki, Koji; Aoyagi, Yoshinobu

doi:10.1143/jjap.45.3988

Cited by 51 publications

(56 citation statements)

References 32 publications

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“…These phenomena did not depend on the KOH concentrations. The etching mechanism can be explained by the actions of hydroxide ions (OH) at the m plane surface [14], similar to the etching mechanism at the -c plane proposed by Li et al [15].…”

Section: Etching Propertiessupporting

confidence: 59%

Fabrication of GaN‐based striped structures along the <11$ \bar 2 $0> direction by the combination of RIE dry‐etching and KOH wet‐etching techniques to recover dry‐etching damage

Itoh

Kinoshita

Kawasaki

et al. 2006

Phys. Status Solidi (c)

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GaN-based striped structures were fabricated using Al 0.2 Ga 0.8 N/GaN single heterostructure by combination of dry/wet etching with taking into account GaN crystal structure. After following wet-etching, the sidewalls of striped structures along the <11 2 0> direction became very smooth and straight compared with that of as dry-etched. We estimated mobility of electron in field effect transistors (FETs) consists striped structures along the <11 2 0> direction from I-V characteristics. The mobility of the as dry-etched striped structures was drastically reduced from the not-patterned Al 0.2 Ga 0.8 N/GaN single heterostructure. In contrast, the mobility of the smooth striped structure FETs were effectively recovered to that of the notpatterned one. These results suggest that following KOH wet-etching can remove the damaged/rough layer indued by the RIE dry-etching.

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Section: Etching Propertiessupporting

confidence: 59%

Fabrication of GaN‐based striped structures along the <11$ \bar 2 $0> direction by the combination of RIE dry‐etching and KOH wet‐etching techniques to recover dry‐etching damage

Itoh

Kinoshita

Kawasaki

et al. 2006

Phys. Status Solidi (c)

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“…We can also observe in Fig. 5 that the sidewall of the a-plane (11)(12)(13)(14)(15)(16)(17)(18)(19)(20) should only be formed by etching the inclined plane of the a-plane (11)(12)(13)(14)(15)(16)(17)(18)(19)(20)(21)(22) first.…”

Section: Resultsmentioning

confidence: 76%

“…According to Stocker and Schubert's [20] result in 1998, KOH mainly produces {10-1-1}-plane and {10-10}-plane in GaN materials. The etching mechanism of KOH on the GaN has been studied [15,21], and we have observed that different morphology formations are created by different polarities and surface bonds [22,23]. However, these literatures pay less attention to the aspect of etching mechanism and do not have sufficient experimental evidence in support of their conclusions.…”

Section: Introductionmentioning

confidence: 97%

The study of wet etching on GaN surface by potassium hydroxide solution

et al. 2016

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Potassium hydroxide solution was used to etch un-doped GaN grown on the sapphire substrate at 180 and 260°C. We illustrated the etching phenomenon in detail and probed its mechanism in the wet etching process. By multiplying the planar density and the number of dangling bonds on the N atom, we proposed the etching barrier index (EBI) to describe the difficulty degree of each lattice facet. The raking of EBI will be ?cCombining the EBI with SEM results, we thoroughly studied the whole etching process. We confirmed that in our research, KOH wet etching on GaN starts from the r-plane instead of the ?c-plane or -c-plane, which differs from other studies. We also found that during the high-temperature etching process, there are two etching approaches. In one, the etching begins vertically from the top to the bottom, then horizontally, and finally reversely from the bottom to the top. In the other, etching pits will develop into a hexagonal hole of the sidewall of m-plane.

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“…Similar results are reported by a number of previous studies on wet chemical etching of GaN using alkaline solution. [25][26][27][28] Etching-rate difference on crystallographic face is qualitatively explained by the difference of dangling bond density (DBD), which is a function of surface energy. 25,26 The DBDs of the (0001) and {1−100} planes are 11.4 and 12.1 nm −2 , respectively, which is smaller than those of the other planes (e.g., {11−20} plane (14.0 nm −2 ) and {1−101} plane (16.0 nm −2 )), indicating that these planes are relatively stable toward wet chemical etching.…”

Section: Resultsmentioning

confidence: 99%

Precise Structural Control of GaN Porous Nanostructures Utilizing Anisotropic Electrochemical and Chemical Etching for the Optical and Photoelectrochemical Applications

Kumazaki

Matsumoto

Sato

2017

J. Electrochem. Soc.

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A low-damaged wet process utilizing electrochemical (EC) etching and subsequent chemical etching has been developed for the fabrication of GaN porous structures. Superior controllability in depth and diameter could be obtained by achieving anisotropic nature of the vertical direction to the substrate by EC etching and horizontal direction by tetramethylammonium hydroxide (TMAH) etching, respectively. The optical and photoelectrochemical properties of GaN porous structures were very sensitive to the structural properties. Photoreflectance measurement revealed that porous sample had an effective refractive index that could be controlled by TMAH etching time. In photoelectrochemical measurement, the incident-photon-to-current conversion efficiency (IPCE) was dramatically enhanced to as high as 91% by the formation of porous structures. A series of experimental results were consistently explained by the change of thickness of pore wall and width of space charge region. Gallium nitride (GaN) and its alloys are getting much attention as building block materials for electrochemical (EC) energy conversion systems such as chemical sensors, water splitting, and artificial photosynthesis because of their attractive features including superior chemical stability, direct transition, and widely tunable bandgap by alloying.1-4 Among the various techniques for improving their conversion efficiency, porosification utilizing EC reactions is one of the most powerful because a high-density array of pores exhibits high specific surface area, low reflectance, and high absorptance properties. 5,6 In addition, this technique is performed at room temperature and does not require any complicated process such as lithography, indicating lower damage and higher productivity than other nanostructure fabrication techniques such as reactive ion etching and selective-area growth. 7-10Many reports involving porosification use photo-assisted EC etching utilizing charge carriers generated by band-edge absorption. 11-14Our group has also succeeded in forming GaN porous nanostructures by photo-assisted EC etching and found the energy-conversion efficiency to be enhanced compared with the planar substrate. 15 However, the pore depth could not be controlled linearly by etching time, resulting in difficulty with forming pores deeper than a micro-meter. This was because charge carriers, most of which were generated near the top surface, were expended preferentially in the lateral etching of pore walls that appeared on the top surface. Such insufficient anisotropic nature makes it difficult to improve structural controllability and form pores deeper than a micro-meter.In this study, we aimed to develop anisotropic EC etching by utilizing charge carriers generated by the avalanche effect as a porosification process. We also investigated a combination of EC etching and subsequent wet chemical etching to further improve the structural controllability. Optical characterization such as photoluminescence (PL), photoreflectance, and photoelectrochemical measure...

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Straight and Smooth Etching of GaN (1100) Plane by Combination of Reactive Ion Etching and KOH Wet Etching Techniques

Cited by 51 publications

References 32 publications

Fabrication of GaN‐based striped structures along the <11$ \bar 2 $0> direction by the combination of RIE dry‐etching and KOH wet‐etching techniques to recover dry‐etching damage

Fabrication of GaN‐based striped structures along the <11$ \bar 2 $0> direction by the combination of RIE dry‐etching and KOH wet‐etching techniques to recover dry‐etching damage

The study of wet etching on GaN surface by potassium hydroxide solution

Precise Structural Control of GaN Porous Nanostructures Utilizing Anisotropic Electrochemical and Chemical Etching for the Optical and Photoelectrochemical Applications

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