Light emitting diode having enhanced side emitting capability
A LED structure with enhanced side-emitting capability is provided. An embodiment of The LED structure comprises, on top of a substrate, a metallic layer, a non-alloy ohmic contact layer, a thick transparent layer, a light generating structure, sequentially arranged in the this order from bottom to top. The metallic layer functions a reflective mirror and is made of a pure metal or a metal nitride for superior reflectivity. The non-alloy ohmic contact layer is interposed between the light generating structure and the metallic layer so as to achieve the required low resistance electrical conduction. The thick transparent layer extracts a significant portion of the light to the sides of the LED structure. The thick transparent layer, made of a semiconductor material or a dielectric material having an refractive index between 1.5 to 3.5, could be located either above, below or both above and below the light generating structure.
1 . A light emitting diode structure, comprising:
a substrate;
a metallic layer above said substrate;
a non-alloy ohmic contact layer above said metallic layer;
a light generating structure above said non-alloy ohmic contact layer; and
a thick transparent layer positioned at least in one of the following locations:
above said light generating structure, and between said light generating structure and said non-alloy ohmic contact layer.
2 . The light emitting diode structure according to claim 1 , wherein said metallic layer is made of one of a pure metal and a metal nitride.
3 . The light emitting diode structure according to claim 2 , wherein said metallic layer is made of one of the following materials: Au, Al, Ag, TiN x , and ZrN x.
4 . The light emitting diode structure according to claim 1 , further comprising an optically transparent and electrically conductive dielectric layer positioned between said metallic layer and said non-alloy ohmic contact layer.
5 . The light emitting diode structure according to claim 4 , wherein said dielectric layer is made of a transparent conductive oxide.
6 . The light emitting diode structure according to claim 5 , wherein said dielectric layer is made of one of the following materials: ITO, IZO, SnO, Antimony-doped SnO, Fluorine-doped SnO, Phosphorus-doped SnO, ZnO, Aluminum-doped ZnO, InO, CdO, CTO, CuAlO, CuCaO, and SrCuO.
7 . The light emitting diode structure according to claim 1 , wherein the thickness of said thick transparent layer is at least 1 μm.
8 . The light emitting diode structure according to claim 1 , wherein said thick transparent layer is at least as thick as said light generating structure.
9 . The light emitting diode structure according to claim 1 , wherein said thick transparent layer is at least as thick as 0.005 times of the lateral dimension of said light generating structure.
10 . The light emitting diode structure according to claim 1 , wherein said thick transparent layer is made of one of a semiconductor material and a dielectric material, having a refractive index between 1.5 and 3.5 and a bandgap larger than the light energy emitted from said light generating structure.
11 . The light emitting diode structure according to claim 10 , wherein said thick transparent layer is made of one of the following materials: AlP, GaP, AlN, AlAs, AlGaP, GaAsP, AlGaAs, and Al l-x Ga x In y P (x≦0.5, 0<y ≦l ).
12 . The light emitting diode structure according to claim 1 , wherein said non-alloy ohmic contact layer is a made of a doped semiconductor material.
13 . The light emitting diode structure according to claim 12 , wherein said non-alloy ohmic contact layer is made of one of the following materials: carbon-doped AlAs, carbon-doped GaP, carbon-doped AIP, carbon-doped AlGaAs, carbon-doped InAlAs, carbon-doped InGaP, carbon-doped InAIP, carbon-doped AlGaP, carbon-doped GaAsP, carbon-doped AlAsP, carbon-doped AlGaInP, carbon-doped AlGaInAs, carbon-doped InGaAsP, carbon-doped AlGaAsP, carbon-doped AlInAsP, carbon-doped InGaAlAsP, Mg-doped AlAs, Mg-doped GaP, Mg-doped AIP, Mg-doped AlGaAs, Mg-doped InAlAs, Mg-doped InGaP, Mg-doped InAIP, Mg-doped AlGaP, Mg-doped GaAsP, Mg-doped AlAsP, Mg-doped AlGaInP, Mg-doped AlGaInAs, Mg-doped InGaAsP, Mg-doped AlGaAsP, Mg-doped AlInAsP, Mg-doped InGaAlAsP, Zn-doped AlAs, Zn-doped GaP, Zn-doped AIP, Zn-doped AlGaAs, Zn-doped InAlAs, Zn-doped InGaP, Zn-doped InAIP, Zn-doped AlGaP, Zn-doped GaAsP, Zn-doped AlAsP, Zn-doped AlGaInP, Zn-doped AlGaInAs, Zn-doped InGaAsP, Zn-doped AlGaAsP, Zn-doped AlInAsP, Zn-doped InGaAlAsP, carbon-doped InP, carbon-doped InAs, carbon-doped GaAs, carbon-doped InAsP, Mg-doped InP, Mg-doped InAs, Mg-doped GaAs, Mg-doped InAsP, carbon-doped InP, Zn-doped InAs, Zn-doped GaAs, and Zn-doped InAsP.
14 . The light emitting diode structure according to claim 1 , wherein said non-alloy ohmic contact layer has a plurality of recesses along the surface facing said metallic layer.