Optical semiconductor device and method of fabricating the same

A method of fabricating an optical semiconductor device including an optical waveguide having a thickness varying in a lengthwise direction thereof, comprising the steps of:

• (a) forming a pair of dielectric masks on a compound semiconductor substrate, said masks including a portion where a width thereof varies in said direction;
• (b) epitaxially growing a lower optical confinement layer by metal-organic vapor phase epitaxy (MOVPE) selective growth;
• (c) forming a quantum well structure by epitaxially growing a quantum well layer or a plurality of quantum well layers with barrier layers sandwiched between said quantum well layers by metal-organic vapor phase epitaxy (MOVPE) selective growth;
• and
• (d) epitaxially growing an upper optical confinement layer by metal-organic vapor phase epitaxy (MOVPE) selective growth,
• said quantum well layer(s) being grown in said step (c) employing tertiarybutylarsine (TBA) and tertiarybutylphosphine (TBP) having a V/III ratio equal to or greater than 50.

A method of fabricating an optical semiconductor device including an optical waveguide, comprising the steps of:

• (a) forming a pair of dielectric masks on a compound semiconductor substrate, said masks including a portion where a width thereof varies in a lengthwise direction of said optical waveguide;
• (b) selectively growing a lower confinement layer by metal-organic vapor phase epitaxy (MOVPE);
• (c) selectively growing a quantum well layer or a plurality of quantum well layers with barrier layers sandwiched between said quantum well layers, of a quantum well structure on said compound substrate by MOVPE;
• and
• (d) selectively growing an upper confinement layer by MOVPE;
• said step of selectively growing a quantum well layer or a plurality of quantum well layers of said quantum well structure providing a band-gap energy which is constant within ±30 meV in said lengthwise direction, and steps (b), (c) and (d) collectively providing an optical waveguide having a thickness varying in said lengthwise direction to thereby have a function of spot-size conversion.

A method of fabricating an optical semiconductor device including an optical waveguide, comprising the steps of:

• (a) forming a pair of dielectric masks on a compound semiconductor substrate, said masks including a portion where a width thereof varies in a lengthwise direction of said optical waveguide;
• (b) selectively growing a lower confinement layer by metal-organic vapor phase epitaxy (MOVPE);
• (c) selectively growing a quantum well layer or a plurality of quantum well layers with barrier layers sandwiched between said quantum well layers, of a quantum well structure on said compound substrate by MOVPE, said quantum well structure having a constant thickness in said lengthwise direction;
• and
• (d) selectively growing an upper confinement layer by MOVPE;
• said lower and upper confinement layers selectively growing in steps (b) and (d) to a thickness varying in said lengthwise direction.

A method of fabricating an optical semiconductor device including an optical waveguide having a thickness varying in a lengthwise direction thereof, comprising the steps of:

• (a) forming a pair of dielectric masks on a compound semiconductor substrate, said masks including a portion where a width thereof varies in said lengthwise direction;
• (b) selectively growing a lower confinement layer, forming a lower optical confinement layer having a thickness varying in said lengthwise direction, by metal-organic vapor phase epitaxy (MOVPE);
• (c) forming a quantum well structure by epitaxially growing a quantum well layer or a plurality of quantum well layers with barrier layers sandwiched between said quantum well layers by MOVPE, epitaxially growing each quantum well layer with a thickness substantially constant in said lengthwise direction;
• and
• (d) selectively growing an upper confinement layer, forming an upper optical confinement layer having a thickness varying in said lengthwise direction, by MOVPE.