Edge-emitting type semiconductor laser

An edge-emitting type semiconductor laser in which a laser cavity is formed by depositing plural semiconductor layers on a crystal growth substrate, comprising:

• an n-type contact layer having a thinner portion formed at least a part right under said laser cavity and a thicker portion except for said thinner portion;
• and
• a concave part which is formed at the bottom of said laser cavity by removing said crystal growth substrate and said plural semiconductor layers existing at least right beneath said laser cavity from the back surface of said crystal growth substrate;
• wherein
• a removing process is carried out until a thickness of said thinner portion of said n-type contact layer becomes thinner than a value Λ of a function of a luminous wavelength λ, determined by the formula
• “Λ=f(λ)=λ(n2−nep2)−1/2/2”
• in which λ, n, and neq are represented by:
• luminous wavelength of an active layer;
• refractive index of said n-type contact layer which depends on said luminous wavelength λ;
• and
• equivalent refractive index of said n-type contact layer in guided wave mode which depends on said luminous wavelength λ.

An edge-emitting type semiconductor in which a laser cavity is formed by depositing plural semiconductor layers on a crystal growth substrate, comprising:

• a substrate;
• an n-type contact layer formed on or above said substrate;
• and
• an active layer formed on or above said n-type contact layer;
• wherein a thickness of at least a part of said n-type contact layer which is right under said laser cavity is thinner than a value Λ of a function of a luminous wavelength λ, determined by the formula
• “Λ=f(λ)=λ(n2−nep2)−1/2/2”
• in which λ, n, and neq are represented by:
• luminous wavelength in said active layer;
• refractive index of said n-type contact layer which depends on said luminous wavelength λ;
• and
• equivalent refractive index of said n-type contact layer in guided wave mode which depends on said luminous wavelength λ, and
• wherein a concave part or a cavity part is formed at least a part right under said laser cavity;
• the semiconductor laser further comprising an n-type clad layer wherein a dielectric film or a semiconductor film having smaller refractive index than that of said n-type clad layer is formed at the bottom of said n-type contact layer exposed in said concave part.

An edge-emitting type semiconductor in which a laser cavity is formed by depositing plural semiconductor layers on a crystal growth substrate, comprising:

• a concave part which is formed at the bottom of said laser cavity by removing said crystal growth substrate and said plural semiconductor layers existing at least right beneath said laser cavity from the back surface of said crystal growth substrate;
• wherein
• a removing process is carried out until a thickness of an n-type contact layer becomes thinner than a value Λ of a function of a luminous wavelength λ, determined by the formula
• “Λ=f(λ)=λ(n2−nep2)−1/2/2”
• in which λ, n, and neq are represented by:
• luminous wavelength of an active layer;
• refractive index of said n-type contact layer which depends on said luminous wavelength λ;
• and
• equivalent refractive index of said n-type contact layer in guided wave mode which depends on said luminous wavelength λ;
• said semiconductor laser further comprising an n-type clad layer wherein a dielectric film or a semiconductor film having smaller refractive index than that of said n-type clad layer is formed at the bottom of said n-type contact layer exposed in said concave part.

An edge-emitting type semiconductor laser in which a laser cavity is formed by depositing plural semiconductor layers on a crystal growth substrate, comprising:

• a substrate;
• an n-type contact layer formed on or above said substrate;
• and
• an active layer formed on or above said n-type contact layer;
• wherein
• a thickness of at least a part of said n-type contact layer which is right under said laser cavity is thinner than a value Λ of a function of a luminous wavelength λ, determined by the formula
• “Λ=f(λ)=λ(n2−nep2)−1/2/2”
• in which λ, n, and neq are represented by:
• luminous wavelength of an active layer;
• refractive index of said n-type contact layer which depends on said luminous wavelength λ;
• and
• equivalent refractive index of said n-type contact layer in guided wave mode which depends on said luminous wavelength λ;
• and wherein the semiconductor laser further comprises:
• a negative electrode formed on the exposed surface of said n-type contact layer whose upper surface is exposed through etching treatment from the upper side of said plural semiconductor layers;
• and
• a semiconductor layer comprising a p-type or undoped Group III nitride compound semiconductor formed between said n-type contact layer and said crystal growth substrate.

An edge-emitting type semiconductor laser in which a laser cavity is formed by depositing plural semiconductor layers on a crystal growth substrate, comprising:

• a substrate;
• an n-type contact layer formed on or above said substrate;
• and
• an active layer formed on or above said n-type contact layer;
• wherein a thickness of at least a part of said n-type contact layer which is right under said laser cavity is thinner than a value Λ of a function of a luminous wavelength λ, determined by the formula
• “Λ=f(λ)=λ(n2−nep2)−1/2/2”
• in which λ, n, and neq are represented by:
• luminous wavelength in said active layer;
• refractive index of said n-type contact layer which depends on said luminous wavelength λ;
• and
• equivalent refractive index of said n-type contact layer in guided wave mode which depends on said luminous wavelength λ;
• said semiconductor laser further comprising:
• a concave part which reaches said n-type contact layer from the back surface of said crystal growth substrate and exists at least right beneath said laser cavity;
• a negative electrode formed on the exposed surface of said n-type contact layer whose upper surface is exposed through etching treatment from the upper side of said plural semiconductor layers;
• and
• a semiconductor layer comprising a p-type or undoped Group III nitride compound semiconductor formed between said n-type contact layer and said crystal growth substrate.

An edge-emitting type semiconductor laser in which a laser cavity is formed by depositing plural semiconductor layers on a crystal growth substrate, comprising:

• a concave part which is formed at the bottom of said laser cavity by removing said crystal growth substrate and said plural semiconductor layers existing at least right beneath said laser cavity from the back surface of said crystal growth substrate;
• wherein
• removing process is carried out until thickness of an n-type contact layer becomes thinner than a value Λ of a function of a luminous wavelength λ, determined by the formula
• “Λ=f(λ)=λ(n2−nep2)−1/2/2”
• in which λ, n, and neq are represented by:
• luminous wavelength of an active layer;
• refractive index of said n-type contact layer which depends on said luminous wavelength λ;
• and
• equivalent refractive index of said n-type contact layer in guided wave mode which depends on said luminous wavelength λ,
• a negative electrode formed on the exposed surface of said n-type contact layer whose upper surface is exposed through etching treatment from the upper side of said plural semiconductor layers;
• and
• a semiconductor layer comprising a p-type or undoped Group III nitride compound semiconductor formed between said n-type contact layer and said crystal growth substrate.