Inverted LED structure with improved light extraction
View Patent ↗A light source and method for fabricating the same are disclosed. The light source includes a substrate and a light emitting structure. The substrate has a first surface and a second surface, the second surface including a curved, convex surface with respect to the first surface of the substrate. The light emitting structure includes a first layer of a material of a first conductivity type overlying the first surface, an active layer overlying the first layer, the active layer generating light when holes and electrons recombine therein, and a second layer includes a material of a second conductivity type overlying the active layer and a second surface opposite to the first surface. A mirror layer overlies the light emitting structure.
1. A method of fabricating a light emitting device comprising:
providing a substrate having a first surface and a second surface that are substantially parallel to one another;
fabricating a light emitting structure on said first surface, said light emitting structure comprising:
a first layer of semiconductor material of a first conductivity type deposited on said substrate;
an active layer overlying said first layer; and
a second layer of semiconductor material of an opposite conductivity type from said first conductivity type overlying said active layer; and
etching said second surface of said substrate to provide a curved, convex surface with respect to said first surface, wherein said substrate comprises sapphire or silicon carbide.
2. A method of fabricating a light emitting device comprising
providing a substrate having a first surface and a second surface that are substantially parallel to one another;
fabricating a light emitting structure on said first surface, said light emitting structure comprising:
a first layer of semiconductor material of a first conductivity type deposited on said substrate;
an active layer overlying said first layer; and
a second layer of semiconductor material of an opposite conductivity type from said first conductivity type overlying said active layer; and
etching said second surface of said substrate to provide a curved, convex surface with respect to said first surface,
wherein etching said second surface of said substrate comprises:
depositing a layer of photoresist on said second surface;
patterning said deposited photoresist layer;
heating said photoresist to a temperature at which a surface of said photoresist layer assumes a curved convex shape; and
etching said photoresist layer and said substrate.
3. The method of claim 1 wherein said curved convex surface is chosen such that a light ray generated in said active layer that is initially reflected from said curved convex surface due to internal reflection subsequently strikes said curved convex surface at an angle that is less than the critical angle to said surface at that point on said surface.