LED with improved injection efficiency
A light emitting device and method for making the same is disclosed. The light-emitting device includes an active layer sandwiched between a p-type semiconductor layer and an n-type semiconductor layer. The active layer emits light when holes from the p-type semiconductor layer combine with electrons from the n-type semiconductor layer therein. The active layer includes a number of sub-layers and has a plurality of pits in which the side surfaces of a plurality of the sub-layers are in contact with the p-type semiconductor material such that holes from the p-type semiconductor material are injected into those sub-layers through the exposed side surfaces without passing through another sub-layer. The pits can be formed by utilizing dislocations in the n-type semiconductor layer and etching the active layer using an etching atmosphere in the same chamber used to deposit the semiconductor layers without removing the partially fabricated device.
1. A light emitting device comprising:
an n-type semiconductor layer, the n-type semiconductor layer including random dislocations;
an active layer comprising a plurality of sub-layers on the n-type semiconductor layer, the active layer including pits of a density between 10 7 cm −2 and 10 10 cm −2 located on the random dislocations, a plurality of the sub-layers having sidewalls that are bounded by the pits and exposed to the pits, bottoms of the pits located in the n-type semiconductor layer;
a p-type semiconductor layer over the active layer, the p-type semiconductor layer extending into the pits and contacting the exposed sidewalls of the sub-layers and an upper surface of the active layer; and
contact electrodes configured to apply a potential difference between the p-type semiconductor layer and the n-type semiconductor layer.
2. The light emitting device of claim 1 , wherein the n-type semiconductor layer is formed on a substrate, the n-type semiconductor layer having a lattice constant that is different from that of a substrate, the difference giving rise to the random dislocations.
3. The light emitting device of claim 1 , wherein the active layer is formed on a c-plane facet of a material in a GaN family of materials.
4. The light emitting device of claim 1 , wherein holes are injected from the p-type semiconductor layer into the active layer, and the active layer and the p-type semiconductor layer are formed so that at least 10 percent of the holes are injected from the p-type semiconductor layer into the active layer through the exposed sidewalls of the sub-layers.
5. The light emitting device of claim 1 , wherein the n-type semiconductor layer and the p-type semiconductor layer comprise GaN family materials.
6. A light emitting device comprising:
an n-type semiconductor layer, the n-type semiconductor layer including random dislocations;
an active layer comprising a plurality of sub-layers on the n-type semiconductor layer, the active layer including pits of a density between 10 7 cm −2 and 10 10 cm −2 located on the random dislocations, a plurality of the sub-layers having sidewalls that are bounded by the pits, bottoms of the pits located in the n-type semiconductor layer;
a p-type semiconductor layer over the active layer, the p-type semiconductor layer extending into the pits and contacting the sidewalls of the sub-layers and an upper surface of the active layer; and
contact electrodes configured to apply a potential difference between the p-type semiconductor layer and the n-type semiconductor layer.
7. The light emitting device of claim 6 , wherein the n-type semiconductor layer is formed on a substrate, the n-type semiconductor layer having a lattice constant that is different from that of a substrate, the difference giving rise to the random dislocations.
8. The light emitting device of claim 6 , wherein the active layer is formed on a c-plane facet of a material in a GaN family of materials.
9. The light emitting device of claim 6 , wherein holes are injected from the p-type semiconductor layer into the active layer, and the active layer and the p-type semiconductor layer are formed so that at least 10 percent of the holes are injected from the p-type semiconductor layer into the active layer through the sidewalls of the sub-layers.
10. The light emitting device of claim 6 , wherein the n-type semiconductor layer and the p-type semiconductor layer comprise GaN family materials.