GaN channel waveguide with vertically polarity inversion formed by surface activated bonding for wavelength conversion

Abstract

We proposed a nitride semiconductor transverse quasi-phase-matched wavelength conversion device with a polarity inverted structure along the vertical direction formed by surface activated bonding and etching processes. Inductively coupled plasma etching of a GaN layer with maintaining a root-mean square roughness of less than 2 nm in a 100 µm square area was achieved even after deep etching of 1 µm using Cl2/Ar mixture gas and optimizing the antenna and bias powers. This smooth etching enabled surface activated bonding of the ultrathin GaN layer with designed thickness. The fabrication process of the GaN polarity inverted channel waveguide was established.

Polarity Inversion of GaN via AlN Oxidation Interlayer Using Metal–Organic Vapor Phase Epitaxy

“…an intermediate layer. [31,32] However, many processes such as adjustment of film thickness and substrate removal are required when fabricating polarity-inverted structures using this technique. Another approach involves polarity inversion via epitaxial growth.…”

“…A thin‐film transfer technique using surface‐activated bonding (SAB) has been reported as a method for fabrication without an intermediate layer. [ 31,32 ] However, many processes such as adjustment of film thickness and substrate removal are required when fabricating polarity‐inverted structures using this technique. Another approach involves polarity inversion via epitaxial growth.…”

Second harmonic generation in GaN transverse quasi-phase-matched waveguide pumped with femtosecond laser

“…13) Recently, we proposed a nitride semiconductor wavelength conversion device with a transverse QPM structure in which the polarity is inverted in the vertical direction. 17) In the transverse QPM channel waveguide, the modal dispersion phase matching condition between a zeroth-order fundamental and a higher-order SH-guided modes is satisfied and the nonlinear coupling coefficient κ is enhanced by inverting the polarity at the nodes of the transverse electric field distribution of the SH wave. [18][19][20] The polarity inverted structure in the transverse QPM wavelength conversion device can be formed by surface activated bonding (SAB) 17,21,22) or epitaxial growth.…”

“…17) In the transverse QPM channel waveguide, the modal dispersion phase matching condition between a zeroth-order fundamental and a higher-order SH-guided modes is satisfied and the nonlinear coupling coefficient κ is enhanced by inverting the polarity at the nodes of the transverse electric field distribution of the SH wave. [18][19][20] The polarity inverted structure in the transverse QPM wavelength conversion device can be formed by surface activated bonding (SAB) 17,21,22) or epitaxial growth. 23,24) It is noted that the waveguide thickness comes to few-hundred nanometers to satisfy the modal dispersion phase matching condition to generate the SH waves in the UV region.…”

“…Thus, in the fabrication process with SAB, the thin GaN layer is formed by once growing a flat layer thicker than 1 μm followed by dry etching maintaining the surface flatness. 17) After the heteroepitaxial layer is transferred by SAB and wafer removal, the epitaxial layer is etched by the dry etching from the back surface. This process has the advantage of removing defective regions near the heterointerface.…”