Light Emitting Device With Undoped Substrate And Doped Bonding Layer
A light emitting device having a stack of layers bonded to an undoped substrate with a doped layer between the stack of layers and the undoped substrate. The stack of layers include a layer of first conductivity type over the doped layer, an overlying light emitting layer and a layer of second conductivity type. In one embodiment, the doped substrate is grown on a sacrificial substrate along with the remaining stack of layers prior to bonding to the undoped substrate. Electrical contacts are coupled to device on a side opposite the undoped substrate. In one embodiment, the layers of first conductivity, the light emitting layer, and the layer of second conductivity are removed to expose the doped layer and a first electrical contact is coupled to the layer of first conductivity through the doped substrate, while a second electrical contact is coupled to the layer of second conductivity.
1 . A light emitting device comprising:
an undoped substrate;
a stack of layers comprising a doped layer, a layer of first conductivity type overlying the doped layer, wherein the doped layer and the layer of first conductivity type are different materials, an active region overlying the layer of first conductivity type, and a layer of second conductivity type overlying the active region, the doped layer having a first side that is bonded to the undoped substrate with the doped layer disposed between the undoped substrate and the layer of first conductivity type; and
a first electrical contact coupled to the layer of first conductivity type and a second electrical contact coupled to the layer of second conductivity type, wherein the doped layer is between the undoped substrate and the first electrical contact and the second electrical contact.
2 . The light emitting device of claim 1 , wherein the undoped substrate is transparent to light emitted by the active region.
3 . The light emitting device of claim 1 , wherein the undoped substrate and the doped layer are formed from the same semiconductor material.
4 . The light emitting device of claim 1 , wherein the undoped substrate and the doped layer are formed from GaP.
5 . The light emitting device of claim 1 , wherein the doped layer provides electrical contact between the first electrical contact and the layer of first conductivity type.
6 . The light emitting device of claim 1 , wherein the active region is between the layer of second conductivity type and the doped layer, the stack of layers further comprising a conductive transparent layer overlying the layer of second conductivity type, wherein the conductive transparent layer forms at least a portion of the second electrical contact with the layer of second conductivity type.
7 . The light emitting device of claim 6 , the stack of layers further comprising a reflective metal layer overlying the conductive transparent layer, wherein the reflective metal layer and the conductive transparent layer form at least a portion of the second electrical contact with the layer of second conductivity type.
8 . A method of forming a light emitting device, the method comprising:
providing a transparent undoped substrate;
forming a stack of layers comprising a layer of first conductivity type, an active region over the layer of first conductivity type, a layer of second conductivity type over the active region, and a doped layer over the layer of second conductivity type, wherein the doped layer and the layer of second conductivity type are different materials,;
bonding the stack of layers to the undoped substrate with the doped layer disposed between the undoped substrate and the layer of second conductivity type;
removing a portion of the layer of first conductivity type, the active region and the layer of second conductivity type to expose the doped layer;
forming a first electrical contact to contact the layer of first conductivity type and a second electrical contact to contact the exposed doped layer, wherein the first electrical contact and second electrical contact are on the same side of the doped layer opposite the undoped substrate.
9 . The method of claim 8 , wherein the undoped substrate and the doped layer are formed from the same semiconductor material.
10 . The method of claim 8 , wherein the undoped substrate and the doped layer are formed from GaP.
11 . The method of claim 8 , wherein the stack of layers are formed on a sacrificial substrate before bonding the stack of layers to the undoped substrate.
12 . The method of claim 11 , wherein the stack of layers are removed from the sacrificial substrate after the stack of layers are bonded to the undoped substrate.
13 . The method of claim 7 , wherein the first electrical contact is at least partially formed by forming a conductive transparent layer over the layer of first conductivity type.
14 . The method of claim 13 , wherein the first electrical contact is further formed by forming a reflective metal layer over the conductive transparent layer.
15 . A light emitting device comprising:
an undoped substrate;
a stack of layers that is bonded to the undoped substrate with a doped layer disposed between the stack of layers and the undoped substrate, the stack of layers comprising a layer of first conductivity type, an active region overlying the layer of first conductivity type, a layer of second conductivity type overlying the active region, wherein the layer of first conductivity type is between the active region and the doped layer, wherein the doped layer and the layer of first conductivity type are different materials; and
a first electrical contact coupled to the layer of first conductivity type and a second electrical contact coupled to the layer of second conductivity type, wherein the doped layer is between the undoped substrate and the first electrical contact and the second electrical contact.
16 . The light emitting device of claim 15 , wherein the undoped substrate is transparent to light emitted by the active region.
17 . The light emitting device of claim 15 , wherein the undoped substrate and the doped layer are formed from the same semiconductor material.
18 . The light emitting device of claim 15 , wherein the undoped substrate and the doped layer are formed from GaP.
19 . The light emitting device of claim 1 , wherein the doped layer provides electrical contact between the first electrical contact and the layer of first conductivity type.
20 . A method of forming a light emitting device, the method comprising:
providing a transparent undoped substrate;
forming a stack of layers comprising a layer of first conductivity type, an active region over the layer of first conductivity type, and a layer of second conductivity type over the active region;
bonding the stack of layers to the undoped substrate with a doped layer disposed between the undoped substrate and the stack of layers, wherein the layer of second conductivity type is between the active region and the doped layer and wherein the doped layer and the layer of second conductivity type are different materials;
removing a portion of the layer of first conductivity type, the active region and the layer of second conductivity type to expose the doped layer;
forming a first electrical contact to contact the layer of first conductivity type and a second electrical contact to contact the exposed doped layer, wherein the first electrical contact and second electrical contact are on the same side of the doped layer opposite the undoped substrate.
21 . The method of claim 20 , wherein the undoped substrate and the doped layer are formed from the same semiconductor material.
22 . The method of claim 20 , wherein the undoped substrate and the doped layer are formed from GaP.
23 . The method of claim 20 , wherein the stack of layers are formed on a sacrificial substrate before bonding the stack of layers to the undoped substrate.
24 . The method of claim 23 , wherein the stack of layers are removed from the sacrificial substrate after the stack of layers are bonded to the undoped substrate.
25 . A light emitting device comprising:
an undoped GaP substrate;
a stack of layers comprising a doped GaP layer, a layer of first conductivity type overlying the doped GaP layer, an active region overlying the layer of first conductivity type, and a layer of second conductivity type overlying the active region, wherein the doped GaP layer is bonded to the undoped GaP substrate; and
the first electrical contact being electrically coupled to the layer of first conductivity type through the doped GaP layer and the second electrical contact being electrically coupled to the layer of second conductivity type, wherein a conductive transparent layer forms at least a portion of the second electrical contact with the layer of second conductivity type and wherein the doped GaP layer is between the undoped GaP substrate and the first electrical contact and the second electrical contact.