Deep ultraviolet LED and method for producing the same

A deep ultraviolet LED with a design wavelength λ, comprising a reflecting electrode layer (Au), a metal layer (Ni), a p-AlGaN contact layer transparent to light with the wavelength λ, a p-block layer made of a p-AlGaN layer, an i-guide layer made of an AlN layer, a multi-quantum well layer, an n-AlGaN contact layer, a u-AlGaN layer, an AlN template, and a sapphire substrate that are arranged in this order from a side opposite to the sapphire substrate,

• wherein:
• a thickness of the p-block layer is 44 to 48 nm,
• a two-dimensional reflecting photonic crystal periodic structure having a plurality of voids is provided in a region from an interface between the metal layer and the p-AlGaN contact layer to a position not beyond an interface between the p-AlGaN contact layer and the p-block layer in a thickness direction of the p-AlGaN contact layer,
• a distance from an end face of each of the voids in a direction of the sapphire substrate to an interface between the multi-quantum well layer and the i-guide layer satisfies λ/2n1Deff (where λ is the design wavelength and n1Deff is the effective average refractive index of each film of the stacked structure from the end face of each void to the i-guide layer) in a perpendicular direction, the distance being in a range of 53 to 61 nm,
• the two-dimensional reflecting photonic crystal periodic structure has a photonic band gap that opens for TE polarized components, and
• provided that a period a of the two-dimensional reflecting photonic crystal periodic structure satisfies a Bragg condition with respect to light with the design wavelength λ, an order m of a formula of the Bragg condition:
• mλ/n2Deff=2a (where m is the order, λ is the design wavelength, n2Deff is an effective refractive index of two-dimensional photonic crystals, and a is the period of the two-dimensional photonic crystals) satisfies 1≤m≤4, and a radius of each void is R, R/a satisfies 0.20R/a0.40.

A deep ultraviolet LED with a design wavelength λ, comprising a reflecting electrode layer (Rh), a p-AlGaN contact layer transparent to light with the wavelength λ, a p-block layer made of a p-AlGaN layer, an i-guide layer made of an AlN layer, a multi-quantum well layer, an n-AlGaN contact layer, a u-AlGaN layer, an AlN template, and a sapphire substrate that are arranged in this order from a side opposite to the sapphire substrate,

• wherein:
• a thickness of the p-block layer is 44 to 48 nm,
• a two-dimensional reflecting photonic crystal periodic structure having a plurality of voids is provided in a region from an interface between the reflecting electrode layer and the p-AlGaN contact layer to a position not beyond an interface between the p-AlGaN contact layer and the p-block layer in a thickness direction of the p-AlGaN contact layer,
• a distance from an end face of each of the voids in a direction of the sapphire substrate to an interface between the multi-quantum well layer and the i-guide layer satisfies λ/2n1Deff (where λ is the design wavelength and n1Deff is the effective average refractive index of each film of the stacked structure from the end face of each void to the i-guide layer) in a perpendicular direction, the distance being in a range of 53 to 61 nm,
• the two-dimensional reflecting photonic crystal periodic structure has a photonic band gap that opens for TE polarized components, and
• provided that a period a of the two-dimensional reflecting photonic crystal periodic structure satisfies a Bragg condition with respect to light with the design wavelength λ, an order m of a formula of the Bragg condition:
• mλ/n2Deff=2a (where m is the order, λ is the design wavelength, n2Deff is an effective refractive index of two-dimensional photonic crystals, and a is the period of the two-dimensional photonic crystals) satisfies 1≤m≤4 and a radius of each void is R, R/a satisfies 0.20R/a0.40.

A method for producing a deep ultraviolet LED with a design wavelength λ, comprising:

• preparing a stacked structure formed on a sapphire substrate as a substrate for growth, the stacked structure including a reflecting electrode layer, a metal layer, a p-GaN contact layer, a p-block layer made of a p-AlGaN layer transparent to light with the wavelength λ, an i-guide layer made of an AlN layer, a multi-quantum well layer, an n-AlGaN contact layer, a u-AlGaN layer, and an AlN template that are arranged in this order from a side opposite to the sapphire substrate, the p-block layer being formed to a thickness of 52 to 56 nm through crystal growth;
• forming a two-dimensional reflecting photonic crystal periodic structure having a plurality of voids in a region from an interface between the metal layer and the p-GaN contact layer to a position not beyond an interface between the p-GaN contact layer and the p-block layer in a thickness direction of the p-GaN contact layer, each of the voids being formed in a position such that a distance from an end face of the void in a direction of the sapphire substrate to an interface between the multi-quantum well layer and the i-guide layer is 53 to 57 nm;
• preparing a mold for forming the two-dimensional reflecting photonic crystal periodic structure;
• forming a resist layer on the p-GaN contact layer and imprinting a structure of the mold to the resist layer through nanoimprinting;
• partially etching the p-GaN contact layer using the resist layer as a mask, thereby forming a two-dimensional photonic crystal periodic structure;
• forming the metal layer in this order on the two-dimensional reflecting photonic crystal structure through oblique deposition;
• and
• forming the reflecting electrode layer on the metal layer.

A method for producing a deep ultraviolet LED with a design wavelength λ, comprising:

• forming a stacked structure on a sapphire substrate as a substrate for growth, the stacked structure including a reflecting electrode layer, a metal layer, a p-AlGaN contact layer transparent to light with the wavelength λ, a p-block layer made of a p-AlGaN layer, an i-guide layer made of an AlN layer, a multi-quantum well layer, an n-AlGaN contact layer, a u-AlGaN layer, and an AlN template that are arranged in this order from a side opposite to the sapphire substrate, the p-block layer being formed to a thickness of 44 to 48 nm through crystal growth;
• forming a two-dimensional reflecting photonic crystal periodic structure having a plurality of voids in a region from an interface between the metal layer and the p-AlGaN contact layer to a position not beyond an interface between the p-AlGaN contact layer and the p-block layer in a thickness direction of the p-AlGaN contact layer, each of the voids being formed in a position such that a distance from an end face of the void in a direction of the substrate for growth to an interface between the multi-quantum well layer and the i-guide layer is 53 to 61 nm;
• preparing a mold for forming the two-dimensional reflecting photonic crystal periodic structure;
• forming a resist layer on the p-AlGaN contact layer and imprinting a structure of the mold to the resist layer through nanoimprinting;
• partially etching the p-AlGaN contact layer using the resist layer as a mask, thereby forming a two-dimensional photonic crystal periodic structure;
• forming the metal layer on the two-dimensional reflecting photonic crystal structure through oblique deposition;
• and
• forming the reflecting electrode layer on the metal layer.

A method for producing a deep ultraviolet LED with a design wavelength λ, comprising:

• forming a stacked structure on a sapphire substrate as a substrate for growth, the stacked structure including a reflecting electrode layer, a p-AlGaN contact layer transparent to light with the wavelength λ, a p-block layer made of a p-AlGaN layer, an i-guide layer made of an AlN layer, a multi-quantum well layer, an n-AlGaN contact layer, a u-AlGaN layer, and an AlN template that are arranged in this order from a side opposite to the sapphire substrate, the p-block layer being formed to a thickness of 44 to 48 nm through crystal growth;
• forming a two-dimensional reflecting photonic crystal periodic structure having a plurality of voids in a region from an interface between the reflecting electrode and the p-AlGaN contact layer to a position not beyond an interface between the p-AlGaN contact layer and the p-block layer in a thickness direction of the p-AlGaN contact layer;
• forming each of the voids in a position such that a distance from an end face of the void in a direction of the substrate for growth to an interface between the multi-quantum well layer and the i-guide layer is 53 to 61 nm;
• preparing a mold for forming the two-dimensional reflecting photonic crystal periodic structure;
• forming a resist layer on the p-AlGaN contact layer and imprinting a structure of the mold to the resist layer through nanoimprinting;
• partially etching the p-AlGaN contact layer using the resist layer as a mask, thereby forming a two-dimensional photonic crystal periodic structure;
• and
• forming the reflecting electrode layer on the two-dimensional reflecting photonic crystal structure through oblique deposition.