Compound semiconductor device and fabrication method of producing the compound semiconductor device

A compound semiconductor device comprising:

• a semiconductor substrate;
• a first growth epitaxial-layer structure formed on said substrate, said first growth epitaxial-layer structure having an epitaxial crystal surface;
• at least one kind of fine uneven structure formed on the entire epitaxial crystal surface of said first growth epitaxial-layer structure, wherein said at least one kind of fine uneven structure comprises at least a diffraction grating which is slanted With respect to a light propagation direction of light propagated in said device so that the diffraction grating has substantially zero diffraction effect for the light;
• and
• a second growth epitaxial-layer structure formed on said fine uneven structure.

A distributed feedback type laser semiconductor device comprising:

• a semiconductor substrate;
• a first growth epitaxial-layer structure formed on said substrate, said first growth epitaxial-layer structure having an epitaxial crystal surface;
• a plurality of kinds of fine uneven structures formed on the entire epitaxial crystal surface of said first growth epitaxial-layer structure;
• a second growth epitaxial-layer structure formed on said plurality of kinds of fine uneven structures;
• and
• an active region formed in one of said first and second growth epitaxial-layer structures,
• wherein at least one of said plurality of kinds of fine uneven structures has an unevenness too small to produce any substantial diffraction effect on any wavelength of light used in said device, and said at least one of said plurality of kinds of uneven structures defines a plurality of surfaces having crystal orientations which are respectively different from a crystal orientation of said first growth epitaxial-layer structure, said plurality of surfaces being adapted to facilitate growth of said second growth epitaxial-layer structure, and another of said plurality of kinds of fine uneven structures is a diffraction grating comprising a distributed feedback reflector and is sufficiently uneven to have a diffraction effect on a wavelength of light to be used in said device.

A distributed Bragg reflection type laser semiconductor device comprising:

• a semiconductor substrate;
• a first growth epitaxial-layer structure formed on said substrate, said first growth epitaxial-layer structure having an epitaxial crystal surface;
• a plurality of kinds of fine uneven structures formed on the entire epitaxial crystal surface of said first growth epitaxial-layer structure;
• a second growth epitaxial-layer structure formed on said plurality of kinds of fine uneven structures;
• and
• an active region formed in one of said first and second growth epitaxial-layer structures,
• wherein at least one of said plurality of kinds of fine uneven structures has an unevenness small enough to produce substantially zero diffraction effect on any wavelength of light used in said device, and said at least one of said plurality of kinds of fine uneven structures defines a plurality of surfaces having crystal orientations which are respectively different from a crystal orientation of said first growth epitaxial-layer structure, said plurality of surfaces being adapted to facilitate growth of said second growth epitaxial-layer structure, and another of said plurality of kinds of fine uneven structures comprises a diffraction grating comprising a distributed Bragg reflector and is sufficiently uneven to have a diffraction effect on a wavelength of light to be used in said device.

An optical compound semiconductor device comprising:

• a semiconductor substrate;
• a first growth epitaxial-layer structure formed on said substrate, said first growth epitaxial-layer structure having an epitaxial crystal surface;
• at least two kinds of fine uneven structures formed on said entire epitaxial crystal surface of said first growth epitaxial-layer structure;
• and
• a second growth epitaxial-layer structure formed on said fine uneven structures,
• wherein said at least two kinds of fine uneven structures include a first fine uneven structure which has an unevenness small enough to produce substantially zero diffraction effect on any wavelength of light used in said device, and said first fine uneven structure defines a plurality of surfaces having crystal orientations which are respectively different from a crystal orientation of said first growth epitaxial-layer structure, said plurality of surfaces being adapted to facilitate growth of said second growth epitaxial-layer structure.

A compound semiconductor device comprising:

• a semiconductor substrate;
• a first growth epitaxial-layer structure formed on said substrate, said first growth epitaxial-layer structure having an epitaxial crystal surface;
• at least two kinds of fine uneven structures on said epitaxial crystal surface of said first growth epitaxial-layer structure, said fine uneven structures being superposed on the common epitaxial crystal surface, wherein said fine uneven structures comprise at least a diffraction grating which is slanted with respect to a light propagation direction of light propagated in the said device so that the diffraction grating has substantially zero diffraction effect for any wavelength of a used light;
• and
• a second growth epitaxial-layer structure formed on said fine uneven structures.

A compound semiconductor device comprising:

• a semiconductor substrate;
• a first growth epitaxial-layer structure formed on said substrate, said first growth epitaxial-layer structure having an epitaxial crystal surface;
• at least two kinds of fine uneven structures on said epitaxial crystal surface of said first growth epitaxial-layer structure, said fine uneven structures being superposed on the common epitaxial crystal surface, wherein said fine uneven structures comprise at least an uneven portion which satisfies at least two conditions of three conditions that said uneven portion is so shallow that said uneven portion has substantially zero diffraction effect for a wavelength of any used light, that said uneven portion has a short pitch which has substantially zero diffraction effect for any wavelength of a used light, and that said uneven portion is slanted with respect to a light propagation direction of light propagated in said device so that said uneven portion has substantially zero diffraction effect for any wavelength of a used light;
• and
• a second growth epitaxial-layer structure formed on said fine uneven structures.

A compound semiconductor device comprising:

• a semiconductor substrate;
• a first growth epitaxial-layer structure formed on said substrate, said first growth epitaxial-layer structure having an epitaxial crystal surface;
• at least two kinds of fine uneven structures on said epitaxial crystal surface of said first growth epitaxial-layer structure, said fine uneven structures being superposed on the common epitaxial crystal surface;
• and
• a second growth epitaxial-layer structure formed on said fine uneven structures;
• and
• a light waveguide, wherein said fine uneven structures comprise a main diffraction grating which has a pitch for imparting a diffraction effect for light propagated in said light waveguide and a sub-diffraction grating which has a pitch for imparting a smaller diffraction effect for the propagated light than said main diffraction grating and is superposed on said main diffraction grating, and wherein said sub-diffraction grating satisfies at least one condition of three conditions that said sub-diffraction grating is so shallow that said sub-diffraction grating has substantially zero diffraction effect for any wavelength of a used light, that said sub-diffraction grating has a short pitch which has substantially zero diffraction effect for any wavelength of a used light, and that said sub-diffraction grating is slanted with respect to a light propagation direction of light propagated in said light waveguide so that said sub-diffraction grating has substantially zero diffraction effect for any wavelength of a used light, and
• wherein a plurality of said light waveguides are layered in a layering direction with a predetermined coupling efficiency, said main and sub-diffraction gratings are formed in the vicinity of one of said light waveguides and electrode means is formed to change a wavelength selectivity between the coupled light waveguides.

A compound semiconductor device comprising:

• a semiconductor substrate;
• a first growth epitaxial-layer structure formed on said substrate, said first growth epitaxial-layer structure having an epitaxial crystal surface;
• at least two kinds of fine uneven structures on said epitaxial crystal surface of said first growth epitaxial-layer structure, said fine uneven structures being superposed on the common epitaxial crystal surface;
• and
• a second growth epitaxial-layer structure formed on said fine uneven structures;
• and
• a light waveguide, wherein said fine uneven structures comprise a main diffraction grating which has a pitch for imparting a diffraction effect for light propagated in said light waveguide and a sub-diffraction grating which has a pitch for imparting a smaller diffraction effect for the propagated light than said main diffraction grating and is superposed on said main diffraction grating, and wherein said sub-diffraction grating satisfies at least one condition of three conditions that said sub-diffraction grating is so shallow that said sub-diffraction grating has substantially zero diffraction effect for any wavelength of a used light, that said sub-diffraction grating has a short pitch which has substantially zero diffraction effect for any wavelength of a used light, and that said sub-diffraction grating is slanted with respect to a light propagation direction of light propagated in said light waveguide so that said sub-diffraction grating has substantially zero diffraction effect for any wavelength of a used light, and
• wherein the pitch of said main diffraction grating is more than ten times the wavelength of the propagated light and the pitch of said sub-diffraction grating is less than the wavelength of the propagated light.

An optical compound semiconductor device comprising:

• a semiconductor substrate;
• a first growth epitaxial-layer structure formed on said substrate, said first growth epitaxial-layer structure having an epitaxial crystal surface;
• at least one kind of fine uneven structure formed on the entire epitaxial crystal surface of said first growth epitaxial-layer structure;
• a second growth epitaxial-layer structure formed on said fine uneven structure;
• wherein said at least one kind of fine uneven structure includes a first fine uneven structure, and said first fine uneven structure satisfies at least one condition of the four conditions shown below so that said first fine uneven structure produces substantially zero diffraction effect on any wavelength of light used in said device,
• (1) that said first fine uneven structure is sufficiently shallow,
• (2) that said first fine uneven structure is a grating whose pitch is sufficiently shorter than any wavelength of light used in said device,
• (3) that said first fine uneven structure is a grating which is slanted with respect to a direction in which light is propagated in said device, and
• (4) that said device further comprises a light waveguide structure and said first fine uneven structure is formed sufficiently away from said light waveguide structure, and
• wherein said first uneven structure defines a plurality of surfaces having a crystal orientations which are respectively different from a crystal orientation of said first growth epitaxial-layer structure, said plurality of surfaces facilitating growth of said second growth epitaxial-layer structure.