Light-emitting device with low forward voltage and method for fabricating the same

A method of fabricating a light-emitting device comprising:

• providing a substrate;
• forming a two-dimensional electron gas (2DEG) structure over the substrate;
• forming an n-type layer over the two-dimensional electron gas structure;
• forming an active region on the n-type layer;
• and
• forming a p-type layer on the active region,
• wherein the step of forming the two-dimensional electron gas structure comprises forming one or more pairs of n-type GaN layers and n-type AlGaN layers, each pair of n-type GaN layer and n-type AlGaN layer is so selected that an interface thereof defines a 2DEG channel;
• and forming a plurality of discontinuities in the two-dimensional electron gas structure exposing the 2DEG channel;
• and
• wherein the n-type layer is in electrical contact with the 2DEG channel through the discontinuities.

A light-emitting device comprising:

• a substrate having an upper surface with recesses or protrusions;
• a two-dimensional electron gas structure formed over the upper surface of the substrate;
• an n-type layer formed on the two-dimensional electron gas (2DEG) structure;
• a p-type layer;
• and
• an active region sandwiched between the n-type layer and the p-type layer,
• wherein the two-dimensional electron gas structure comprises one or more pairs of n-type GaN layers and n-type AlGaN layers, each pair of n-type GaN layer and n-type AlGaN layer is so selected that an interface thereof defines a 2DEG channel, the two-dimensional electron gas structure is vertically displaced in accordance with the recesses or protrusions on the upper surface of the substrate so as to form a plurality of upper portions and a plurality of lower portions, at least some of the 2DEG channels in the upper portions are in electrical contact with the n-type layer.

A method of fabricating a light-emitting device comprising:

• providing a substrate having an upper surface with recesses or protrusions;
• forming a two-dimensional electron gas structure over the substrate;
• forming an n-type layer on the two-dimensional electron gas structure;
• forming an active region on the n-type layer;
• and
• forming a p-type layer on the active region,
• wherein the step of forming the two-dimensional electron gas structure comprises:
• forming one or more pairs of n-type GaN layers and n-type AlGaN layers over the upper surface of the substrate, each pair of n-type GaN layer and n-type AlGaN layer is so selected that an interface thereof defines a 2DEG channel, the two-dimensional electron gas structure is vertically displaced in accordance with the recesses or protrusions on the upper surface of the substrate so as to form a plurality of upper portions and a plurality of lower portions, at least some of the 2DEG channels in the upper portions are exposed by recesses formed between the upper portions and the corresponding lower portions of the two-dimensional electron gas structure and are in electrical contact with the n-type layer.

A light-emitting device comprising:

• an n-type layer;
• a p-type layer;
• a p-type protection layer;
• an active region sandwiched between the n-type layer and the p-type protection layer;
• and
• a two-dimensional hole gas (2DHG) structure formed on the p-type protection layer, wherein the two-dimensional hole gas structure comprises one or more pairs of p-type GaN layers and p-type AlGaN layers, each pair of p-type GaN layer and p-type AlGaN layer is so selected that an interface thereof defines a 2DHG channel;
• wherein a plurality of openings are formed in the two-dimensional hole gas structure exposing the 2DHG channel and the p-type protection layer, and the p-type layer is formed on the two-dimensional hole gas structure filling the openings and electrically connecting the 2DHG channel to the p-type protection layer.