Observation of nanopipes in edge-defined film-fed grown <i>β</i>-Ga<sub>2</sub>O<sub>3</sub> substrate and their effect on homoepitaxial surface hillocks
Tomoka Nishikawa, Ken Goto, Hisashi Murakami, Yoshinao Kumagai, Masahiro Uemukai, Tomoyuki Tanikawa, Ryuji Katayama
Abstract
Abstract β -Ga 2 O 3 substrates and homoepitaxial films were characterized using the multiphoton excitation photoluminescence (MPPL) method. MPPL emission peaks at 3.2 and 3.36 eV were obtained with broad shoulders on the low energy side. MPPL images showed the presence of nanopipes in the substrate with a unique contrast. Three-dimensional MPPL imaging revealed the distribution and spatial location of the nanopipes. All the nanopipes were elongated along the [010] direction with diameters of approximately 0.4–1.0 μ m and lengths of 10–30 μ m. The nanopipes were aligned in the [100] and [001] directions with sub-micron spacing in the (0 <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mover accent="true"> <mml:mn>1</mml:mn> <mml:mo>¯</mml:mo> </mml:mover> </mml:math> 0)-oriented substrate. The nanopipes were located under the hillocks at the homoepitaxial surface. The nanopipes are suggested to trigger the hillock growth by transforming into threading dislocations in the homoepitaxial film.