Light-emitting diode structure
View Patent ↗A gallium-nitride based light-emitting diode structure includes a digital penetration layer to raise its reverse withstanding voltage and electrostatic discharge. The digital penetration layer is formed by alternate stacking layers of Al x In y Ga 1-x-y N z P 1-z /Al p In q Ga 1-p-q N r P 1-r , wherein 0≦x,y,z,p,q,r≦1, and Al x In y Ga 1-x-y N z P 1-z has an energy gap greater than that of Al p In q Ga 1-p-q N r P 1-r . The Al x In y Ga 1-x-y N z P 1-z layers have increasing thickness and the Al p In q Ga 1-p-q N z P 1-r layers have decreasing thickness.
1. A light-emitting diode structure, comprising:
a substrate made of a material selected from a group consisting of Sapphire, 6H-Sic, 4H-Sic, ZnO, GaAs, MgAl 2 O 4 , and a single crystal oxide with a lattice constant close to that of a nitride semiconductor;
a buffer layer formed on said substrate, and made of Al 1-a-b Ga a In b N, wherein 0≦a, b<1, and a+b≦1;
an n-type gallium-nitride contact layer formed on said buffer layer, said n-type gallium-nitride contact layer having 900–1200° C. growth temperature, and 2–5 μm thickness;
a light-emitting stack layer formed on said n-type gallium-nitride contact layer, and made of Al 1-x-y Ga x In y N with 700–900° C. growth temperature, wherein 0<x, y<1, and x+y≦1;
a p-type gallium-nitride contact layer formed on said light-emitting stack layer, said p-type gallium-nitride contact layer having 900–1200° C. growth temperature, and thickness less than 5000 Å;
a digital penetration layer formed on said p-type gallium-nitride contact layer;
a transparent conductive layer formed on said digital penetration layer, and made of a material selected from a group consisting of Ni/Au, Ni/Pt, Ni/Pd, Pd/Au, Pt/Au, Cr/Au, Ni/AuBe, Ni/Cr/Au, Ni/Pt/Au, and Ni/Pd/Au;
a first ohmic contact electrode formed over a portion of said digital penetration layer not covered by said transparent conductive layer to serve as a p-type ohmic contact, said first ohmic contact electrode being made of a material selected from a group consisting of Ni/Au alloy, Ni/Pt alloy, Ni/Pd alloy, Ni/Co alloy, Pd/Au alloy, Pt/Au alloy, Ti/Au alloy, Cr/Au alloy, Sn/Au alloy, Ta/Au alloy, TiN, TiWN x , (x≧0), and WSi y (y≦0); and
a second ohmic contact electrode formed over a portion of said n-type gallium-nitride layer to serve as an n-type ohmic contact, said second ohmic contact electrode being made of a material selected from a group consisting of Ti/Al alloy, Ti/Al/Ti/Au alloy, Ti/Al/Ni/Au alloy, Ti/Al/Pt/Au alloy, Ti/Au alloy, and Cr/Au alloy.
2. The light-emitting diode structure as claimed in claim 1 , wherein said digital penetration layer comprises alternate stacking layers of Al x In y Ga 1-x-y N z P 1-z /Al p In q Ga 1-p-q N r P 1-r with Al x In y Ga 1-x-y N z P 1-z having increasing thickness in a range between 2 Å to 20 Å and Al p In q Ga 1-p-q N r P 1-r having decreasing thickness in a range between 20 Å to 2 Å, wherein 0≦x,y,z,p,q,r≦1, and Al x In y Ga 1-x-y N z P 1-z has an energy gap greater than that of Al p In q Ga 1-p-q N r P 1-r .
3. The light-emitting diode structure as claimed in claim 2 , wherein said digital penetration layer has more than two repetitions of Al x In y Ga 1-x-y N z P 1-r /Al p In q Ga 1-p-q N r P 1-r layers with overall thickness being less than or equal to 100 Å.
4. The light-emitting diode structure as claimed in claim 2 , wherein each layer of said alternate stacking layers of Al x In y Ga 1-x-y N z P 1-z /Al p In q Ga 1-p-q N r P 1-r has electric conduction type being P-type, N-type, or I-type, and said alternate stacking layers may comprise layers with different electric conduction types.
5. The light-emitting diode structure as claimed in claim 1 , wherein said digital penetration layer comprises a first layer made of I-type undoped GaN with 20 Å thickness, a second layer made of N-type InGaN with 5 Å thickness, a third layer made of N-type GaN with 10 Å thickness, a fourth layer made of N-type InGaN with 10 Å thickness, a fifth layer made of N-type GaN with 5 Å thickness, and a sixth layer made of I-type undoped InGaN with 20 Å thickness.
6. A light-emitting diode structure, comprising:
a substrate made of a material selected from a group consisting of Sapphire, 6H-Sic, 4H-Sic, ZnO, GaAs, MgAl 2 O 4 , and a single crystal oxide with a lattice constant close to that of a nitride semiconductor;
a buffer layer formed on said substrate, and made of Al 1-a-b Ga a In b N, wherein 0≦a, b<1, and a+b≦1;
an n-type gallium-nitride contact layer formed on said buffer layer, said n-type gallium-nitride contact layer having 900–1200° C. growth temperature, and 2–5 μm thickness;
a light-emitting stuck layer formed on said n-type gallium-nitride contact layer, and made of Al 1-x-y Ga x In y N with 700–900° C. growth temperature, wherein 0<x, y<1, and x+y≦1;
a p-type gallium-nitride contact layer formed on said light-emitting stack layer, said p-type gallium-nitride contact layer having 900–1200° C. growth temperature, and thickness less than 5000 Å;
a digital penetration layer formed on said p-type gallium-nitride contact layer;
a transparent conductive oxide layer formed on said digital penetration layer, and made of a material selected from a group consisting of ITO, CTO, ZnO, and InO;
a first ohmic contact electrode formed over a portion of said digital penetration layer not covered by said transparent conductive oxide layer to serve as a p-type ohmic contact, said first ohmic contact electrode being made of a material selected from a group consisting of Ni/Au alloy, Ni/Pt alloy, Ni/Pd alloy, Ni/Co alloy, Pd/Au alloy, Pt/Au alloy, Ti/Au alloy, Cr/Au alloy, Sn/Au alloy, Ta/Au alloy, TiN, TiWN x (x≧0), and WSi y (y≧0); and
a second ohmic contact electrode formed over a portion of said n-type gallium-nitride layer to serve as an n-type ohmic contact, said second ohmic contact electrode being made of a material selected from a group consisting of Ti/Al alloy, Ti/Al/Ti/Au alloy, Ti/Al/Ni/Au alloy, Ti/Al/Pt/Au alloy, Ti/Au alloy, and Cr/Au alloy.
7. The light-emitting diode structure as claimed in claim 6 , wherein said digital penetration layer comprises alternate stacking layers of Al x In y Ga 1-x-y N z P 1-z /Al p In q Ga 1-p-q N r P 1-r with Al x In y Ga 1-x-y N z P 1-z having increasing thickness in a range between 2 Å to 20 Å and Al p In q Ga 1-p-q N r P 1-r having decreasing thickness in a range between 20 Å to 2 Å, wherein 0≦x,y,z,p,q,r≦1, and Al x In y Ga 1-x-y N z P 1-z has an energy gap greater than that of Al p In q Ga 1-p-q N r P 1-r .
8. The light-emitting diode structure as claimed in claim 7 , wherein said digital penetration layer has more than two repetitions of Al x In y Ga 1-x-y N z P 1-z /Al p In q Ga 1-p-q N r P 1-r layers with overall thickness being less than or equal to 100 Å.
9. The light-emitting diode structure as claimed in claim 7 , wherein each layer of said alternate stacking layers of Al x In y Ga 1-x-y N z P 1-z /Al p In q Ga 1-p-q N r P 1-r has electric conduction type being P-type, N-type, or I-type, and said alternate stacking layers may comprise layers with different electric conduction types.
10. The light-emitting diode structure as claimed in claim 6 , wherein said digital penetration layer comprises a first layer made of I-type undoped GaN with 20 Å thickness, a second layer made of N-type InGaN with 5 Å thickness, a third layer made of N-type GaN with 10 Å thickness, a fourth layer made of N-type InGaN with 10 Å thickness, a fifth layer made of N-type GaN with 5 Å thickness, and a sixth layer made of I-type undoped InGaN with 20 Å thickness.