Graduate School of Science and Technology, Niigata University^* Department of Environmental Science, Niigata University, Japan^**
○Yo Otaki^* Yu Yanadori^* Yuusuke Seki^* Shoji Kashida^**

The 3-6 compound semiconductor Ga₂Te₃ crystalizes into the zinc-blende structure, where one-third of its cation sites is vacant in order to satisfy the chemical valency. Hanada et al. reported from electron diffraction study that if Ga₂Te₃ is annealed at temperature just below its melting point, vacancies are gathered at every ten layer.
We prepared three types of Ga₂Te₃ samples,1) cooled down slowly 2)quenched 3)annealed. Detailed X-ray intensity data were collected on a four-circle diffractmeter. Weak diffuse streaks appeared between main reflections along the [111] directions and satellite reflections appeared near the main reflections. The crystal 1) shows satellite reflections at q=(0.085,0.05,0.0). An extinction rule was observed: around the (100) type main reflections, satellites appeared only at planes perpendicular to the [100] direction.
An asymmetry exists between a pair of satellites centered about the main reflection. The intensity of the higher angle satellite is stronger than that of the low angle counterpart.
These data indicate that the crystals have long period incommensurate structures, with transverse type modulation coupled with vacancies.