Textured single crystal
A method for fabricating a textured single crystal including depositing pads made of metal on a surface of a single crystal. A protective layer is deposited on the pads and on the single crystal between the pads; and etching the surface with a first compound that etches the metal more rapidly than the protective layer is carried out. Processing continues with etching the surface with a second compound that etches the single crystal more rapidly than the protective layer; and etching the surface with a third compound that etches the protective layer more rapidly than the single crystal. The textured substrate may be used for the epitaxial growth of GaN, AlN or III-N compounds (i.e. a nitride of a metal the positive ion of which carries a +3 positive charge) in the context of the fabrication of LEDs, electronic components or solar cells.
1. Method for fabricating a textured single crystal comprising:
depositing pads comprising metal on a surface of a single crystal;
depositing a protective layer on the pads and on the single crystal between the pads;
etching the surface with a first compound that etches the metal more rapidly than the protective layer;
etching the surface with a second compound that etches the single crystal more rapidly than the protective layer; and
etching the surface with a third compound that etches the protective layer more rapidly than the single crystal.
2. Method according to claim 1 , characterized in that the metal is chosen from Ag, Al, Au, Cr, Cu, In, Mo, Ni, Pt, Sn, Ti, W.
3. Method according to claim 1 , characterized in that the pads are produced by depositing a metal layer followed by a heat treatment at a temperature such that diffusion of the metal layer leads to the pads being formed.
4. Method according to claim 3 , characterized in that the metal layer has a thickness larger than 7 nm.
5. Method according to claim 1 , characterized in that the metal layer has a thickness smaller than 40 nm.
6. Method according to claim 1 , characterized in that the heat treatment is carried out at a temperature higher than T f —650° C., especially T f —750° C., T f being the melting point of the metal.
7. Method according to claim 1 , characterized in that the single crystal is sapphire.
8. Method according claim 7 , characterized in that the first compound and the second compound comprise a solution of sulphuric acid and phosphoric acid.
9. Method according to claim 1 , characterized in that the first compound and the second compound are identical.
10. Method according to claim 1 , characterized in that the protective layer is a silicon-IV compound such as silicon oxide or silicon nitride or an oxynitride of silicon.
11. Method according to claim 1 , characterized in that the thickness of the protective layer lies between 1 and 350 nm.
12. Method according to claim 1 , characterized in that the third compound comprises hydrofluoric acid.