Novel in situ self-separation of a 2 in. free-standing m-plane GaN wafer from an m-plane sapphire substrate by HCl chemical reaction etching in hydride vapor-phase epitaxy

Seohwi Woo; Sangil Lee; Uiho Choi; Hyunjae Lee; Minho Kim; Jaiyong Han; Okhyun Nam

doi:10.1039/c6ce00642f

Novel in situ self-separation of a 2 in. free-standing m-plane GaN wafer from an m-plane sapphire substrate by HCl chemical reaction etching in hydride vapor-phase epitaxy

CrystEngComm ◽

10.1039/c6ce00642f ◽

2016 ◽

Vol 18 (40) ◽

pp. 7690-7695

Author(s):

Seohwi Woo ◽

Sangil Lee ◽

Uiho Choi ◽

Hyunjae Lee ◽

Minho Kim ◽

...

Keyword(s):

Chemical Reaction ◽

Vapor Phase ◽

Sapphire Substrate ◽

Vapor Phase Epitaxy ◽

Hydride Vapor Phase Epitaxy ◽

Free Standing

A 2 in.-diameter free-standing m-plane GaN wafer was fabricated through in situ self-separation from m-plane sapphire using HCl chemical reaction etching (HCRE) in hydride vapor-phase epitaxy (HVPE).

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In-Situ Preparation of GaN Sacrificial Layers on Sapphire Substrate in MOVPE Reactor for Self-Separation of the Overgrown GaN Crystal

Crystals ◽

10.3390/cryst10121100 ◽

2020 ◽

Vol 10 (12) ◽

pp. 1100

Author(s):

Sepideh Faraji ◽

Elke Meissner ◽

Roland Weingärtner ◽

Sven Besendörfer ◽

Jochen Friedrich

Keyword(s):

Vapor Phase ◽

Sapphire Substrate ◽

Vapor Phase Epitaxy ◽

The Self ◽

Etching Process ◽

Hydride Vapor Phase Epitaxy ◽

Etching Parameters ◽

Gan Crystal

GaN layers on sapphire substrates were prepared by using metal organic vapor phase epitaxy (MOVPE) combined with an in-situ H2 etching process for the purpose of later self-separation of thick GaN crystals produced by hydride vapor phase epitaxy (HVPE) on such substrates. The etching process results in deep pits and long voids that formed on the surface and along the lower interface between GaN and sapphire, respectively. The pits, which were investigated by SEM analysis, can be modified in their aspect ratio and density by controlling the etching parameters. Using a proper set of in-situ etching parameters, a seed layer with internal voids can be prepared, which is suitable for HVPE overgrowth and the self-separation process. The quality of the in-situ-etched seed GaN layer and overgrown GaN crystal were characterized by X-ray diffraction (XRD) and defect selective etching (DSE). With the aid of atomic force microscopy (AFM) in tapping mode, the interface morphology of the separated GaN crystal was analyzed. The crystal quality of the separated HVPE-GaN crystal is comparable to the crystal grown on untreated GaN MOVPE-seed, which did not separate from the sapphire substrate. The introduced technique to promote the crystal separation during the HVPE process has no obvious drawback on the quality of the grown GaN crystals. Using this technique, the self-separation occurs more gently due to a weakened interface between GaN/sapphire. The conventional separation from an untreated seed by pure thermomechanical action results in higher mechanical forces on the crystal and consequently much higher risk of crystal breakage.

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