Gallium-nitride based light-emitting diode structure with high reverse withstanding voltage and anti-ESD capability
View Patent ↗An epitaxial structure for GaN-based LEDs to achieve better reverse withstanding voltage and anti-ESD capability is provided. The epitaxial structure has an additional anti-ESD thin layer on top of the p-type contact layer within traditional GaN-based LEDs, which is made of undoped indium-gallium-nitrides (InGaN) or low-band-gap (Eg<3.4 eV), undoped aluminum-indium-gallium-nitrides (AlInGaN). This anti-ESD thin layer greatly improves the GaN-based LEDs' reverse withstanding voltage and resistivity to ESD, which in turn extends the GaN-based LEDs' operation life significantly.
1. A GaN-based LED structure, comprising:
a substrate made of a material selected from the group consisting of sapphire, 6H—SiC, 4H—SiC, Si, ZnO, GaAs, MgAl 2 O 4 , and an oxide monocrystalline having a lattice constant compatible with that of nitride semiconductors;
a buffer layer made of Al a Ga b In 1-a-b N (0≦a,b<1, a+b≦1) having a specific composition located on top of an upper side of said substrate;
an n-type contact layer made of a GaN-based material located on top of said buffer layer;
an active layer made of InGaN located on top of a part of said n-type contact layer's upper surface;
a negative electrode located on top of another part of said n-type contact layer's upper surface not covered by said active layer;
a p-type cladding layer made of a p-type GaN-based material located on top of said active layer;
a p-type contact layer made of p-type GaN located on top of said p-type cladding layer;
an anti-ESD thin layer made of a material selected from the group consisting of undoped InGaN, undoped AlInGaN having a band gap less than 3.4 eV, and a superlattice structure comprising undoped InGaN and undoped AlInGaN having a band gap less than 3.4 eV;
a transparent conductive layer selected from the group consisting of a metallic conductive layer and a transparent oxide layer, located on top of a part of said anti-ESD thin layer's upper surface, wherein said metallic conductive layer is made of a material selected from the group consisting of Ni/Au alloy, Ni/Pt alloy, Ni/Pd alloy, Pd/Au alloy, Pt/Au alloy, Cr/Au alloy, Ni/Au/Be alloy, Ni/Cr/Au alloy, Ni/Pt/Au alloy, and Ni/Pd/Au alloy, and said transparent oxide layer is made of a material selected from the group consisting of ITO, CTO, ZnO:Al, ZnGa 2 O 4 , SnO 2 :Sb, Ga 2 O 3 :Sn, AgInO 2 :Sn, In 2 O 3 :Zn, CuAlO 2 , LaCuOS, NiO, CuGaO 2 , and SrCu 2 O 2 ; and
a positive electrode located on top of another part of said anti-ESD thin layer's upper surface not covered by said transparent conductive layer, made of a material selected from the 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).
2. The GaN-based LED structure as claimed in claim 1 , wherein said anti-ESD thin layer has a thickness between 5 Å and 100 Å, and is made of undoped In d Ga 1-d N (0<d≦1) having a specific composition.
3. The GaN-based LED structure as claimed in claim 1 , wherein said anti-ESD thin layer has a thickness between 5 Å and 100 Å, and is made of undoped Al e In f Ga 1-e-f N (0<e,f<1, e+f<1) having a specific composition and a band gap less than 3.4 eV.
4. The GaN-based LED structure as claimed in claim 1 , wherein said anti-ESD layer has a thickness no more than 200 Å and has a superlattice structure formed by alternately stacking a InGaN thin layer and a AlInGaN thin layer repetitively with a repetition count at least two, wherein each of said InGaN thin layers has a thickness between 5 Å and 20 Å, and is made of undoped In k Ga 1-k N (0<k≦1) having a specific composition, and each of said AlInGaN thin layers has a thickness between 5 Å and 20 Å, and is made of undoped Al p In q Ga 1-p-q N (0<p,q<1, p+q<1) having a specific composition and a band gap less than 3.4 eV.