PHOTONIC CRYSTALS IN MICRO LIGHT-EMITTING DIODE DEVICES
Embodiments relate to a micro light emitting diode (LED) having photonic crystal columns extending from a surface to the opposite surface of a transparent semiconductor layer to increase directionality of the light emitted from the micro LED. The photonic crystal columns are arranged in two-dimension. The photonic crystal columns can be produced by etching the transparent semiconductor layer with plasma and growing the photonic crystal columns in the transparent semiconductor layer. The photonic crystal columns can also be produced by etching nano-meter scale regions of the transparent semiconductor layer.
1 . A light emitting diode comprising:
a transparent P-type semiconductor layer;
a quantum well region on the transparent P-type semiconductor layer and configured to emit light responsive to passing current through the quantum well region;
a transparent N-type semiconductor layer having a first surface abutting the quantum well region and a second surface facing away from the quantum well region; and
a plurality of photonic crystal columns extending from the first surface to the second surface to receive light from the quantum well region.
2 . The light emitting diode of claim 1 , where the quantum well region is not physically etched.
3 . The light emitting diode of claim 1 , where the photonic crystal columns come in contact with the quantum well region and no etching is performed in the quantum well region.
4 . The light emitting diode of claim 1 , where the photonic crystal columns are separated from the quantum well region by a distance that is shorter than a wavelength of the light.
5 . The light emitting diode of claim 1 , where the photonic crystal columns are configured to inhibit propagation of the light in predetermined directions to reduce divergence of the light.
6 . The light emitting diode of claim 1 , further comprising an interposer comprising a plurality of electrically conducting wires connected between electrodes on the transparent P-type semiconductor layer and electrodes of an electrical circuit on a silicon semiconductor substrate.
7 . The light emitting diode of claim 1 , wherein the photonic crystal columns are produced by etching the transparent N-type semiconductor layer with plasma.
8 . The light emitting diode of claim 1 , wherein the transparent P-type semiconductor is P-GaN.
9 . The light emitting diode of claim 1 , wherein the transparent N-type semiconductor is N-GaN semiconductor comprising a layer of undoped GaN.
10 . A method for producing a light emitting diode, comprising:
sandwiching a layer of semiconductor material between a P-type semiconductor layer and a transparent N-type semiconductor layer to fabricate a quantum well region that emit light responsive to passing current through the quantum well region;
etching through a plurality of selective regions of the transparent N-type semiconductor layer to form gaps in the transparent N-type semiconductor layer; and
growing a plurality of photonic crystal columns in the gaps in the transparent N-type semiconductor layer, the photonic crystal columns configured to receive light from the quantum well region.
11 . The method of claim 10 , where the photonic crystal columns come in contact with the quantum well region and no etching is performed in the quantum well region.
12 . The method of claim 10 , where the photonic crystal columns are separated from the quantum well region by a distance that is shorter than a wavelength of the light.
13 . The method of claim 10 , where the photonic crystal columns are configured to inhibit propagation of the light in predetermined directions to reduce divergence of the light.
14 . The method of claim 10 , further comprising:
placing an interposer between electrodes on the transparent P-type semiconductor layer and electrodes of an electrical circuit on a silicon semiconductor substrate.
15 . The method of claim 10 , wherein etching through the plurality of selective regions is performed by exposing the selective regions to plasma.
16 . The method of claim 10 , wherein growing a plurality of photonic crystal columns in the gaps in the transparent N-type semiconductor layer comprises:
attaching a two-dimensional microporous silicon membrane on the quantum well region in the gaps of the transparent N-type semiconductor layer;
growing the photonic crystal columns in an epitaxial deposition chamber; and
removing the two-dimensional microporous silicon membrane after growing the photonic crystal columns.
17 . A method for producing a light emitting diode, comprising:
sandwiching a layer of semiconductor material between a P-type semiconductor layer and a transparent N-type semiconductor layer to fabricate a quantum well region that emits light responsive to passing current through the quantum well region;
placing a mask on the transparent N-type semiconductor layer, the mask comprising nano-meter scale periodic gaps; and
etching unmasked regions of the transparent N-type semiconductor layer to form a plurality of photonic crystal columns in the transparent N-type semiconductor layer, the photonic crystal columns configured to receive light from the quantum well region.
18 . The method of claim 17 , where the photonic crystal columns come in contact with the quantum well region and where no etching is performed in the quantum well region.
19 . The method of claim 17 , where the photonic crystal columns are configured to inhibit propagation of the light in predetermined directions to reduce divergence of the light.
20 . The method of claim 17 , further comprising:
placing an interposer between electrodes on the transparent P-type semiconductor layer and electrodes of an electrical circuit on a silicon semiconductor substrate.