LED sidewall processing to mitigate non-radiative recombination
LEDs and methods of forming LEDs with various structural configurations to mitigate non-radiative recombination at the LED sidewalls are described. The various configurations described include combinations of LED sidewall surface diffusion with pillar structure, modulated doping profiles to form an n-p superlattice along the LED sidewalls, and selectively etched cladding layers to create entry points for shallow doping or regrowth layers.
1. A light emitting structure comprising:
a body including:
a first cladding layer doped with a first dopant type;
a barrier layer; and
an active layer between the first cladding layer and the barrier layer;
a pillar structure that protrudes from a first surface of the body, wherein the pillar structure includes a second cladding layer doped with a second dopant type opposite the first dopant type;
a center vertical axis that extends through the body and pillar structure; and
a current confinement region dopant concentration of the second dopant type characterized by a vertical depth that extends from the first surface of the body and through the barrier layer, the active layer, and into the first cladding layer, while additionally encroaches from sidewalls of the body including the barrier layer, the active layer, and at least a portion of the first cladding layer toward the center vertical axis.
2. The light emitting structure of claim 1 , wherein the first dopant type is n-type, the second dopant type is p-type.
3. The light emitting structure of claim 2 , wherein the current confinement region dopant concentration is formed of a dopant selected from the group consisting of Mg and Zn.
4. The light emitting structure of claim 1 , further comprising:
a conformal passivation layer formed on and spanning the sidewalls of the body, sidewalls of the pillar structure, and a surface of the pillar structure opposite the body;
an opening in the conformal passivation layer on the surface of the pillar structure; and
a conductive contact formed on the surface of the pillar structure and within the opening of the conformal passivation layer.
5. The light emitting structure of claim 4 , further comprising a second conductive contact over the first cladding layer.
6. The light emitting structure of claim 5 , wherein the conductive contact is bonded to a contact pad on a display substrate with a solder material.
7. The light emitting structure of claim 1 , wherein the first dopant type is n-type, the second dopant type is p-type, and the pillar structure includes a p-type contact layer underneath the second cladding layer.
8. The light emitting structure of claim 7 , wherein the p-type contact layer comprises GaP or GaAs.
9. The light emitting structure of claim 8 , further comprising a bottom conductive contact on a bottom surface of the pillar structure.
10. The light emitting structure of claim 1 , wherein the first dopant type is n-type, the second dopant type is p-type, and the second cladding layer comprises AlGaInP.
11. The light emitting structure of claim 10 , wherein the barrier layer comprises AlGaInP.
12. The light emitting structure of claim 11 , wherein the second cladding layer comprises an AlGaInP alloy with a higher Aluminum content than an AlGaInP alloy in the barrier layer.
13. The light emitting structure of claim 12 , wherein the barrier comprises an (Al x Ga 1-x ) 0.5 In 0.5 P alloy with 0.5≤x≤0.8.
14. The light emitting structure of claim 13 , wherein the second cladding layer comprises an (Al x Ga 1-x ) 0.5 In 0.5 P alloy with 0.6≤x≤1.0.
15. The light emitting structure of claim 10 , wherein the current confinement region dopant concentration is formed of a Zn dopant.
16. The light emitting structure of claim 15 , wherein the second cladding layer is doped with Mg.
17. The light emitting structure of claim 1 , wherein the active layer includes one or more bulk active layers separated by spacer layers.