Light-emitting diode
View Patent ↗A light-emitting diode, comprises an active layer for emitting a light with a phase and a peak wavelength λ in air, a reflector, a lower semiconductor stack between the active layer and the reflector, wherein the lower semiconductor stack comprises multiple semiconductor layers, and each of the multiple semiconductor layers has a refractive index ni, a thickness di and two sides each contacting adjacent layers to form two interfaces, wherein each interface has a phase shift when the light passes through the interface.
1. A light-emitting diode, comprising:
an active layer for emitting a light ray with a phase and a peak wavelength λ in air;
an upper semiconductor stack on the active layer;
a reflector; and
a lower semiconductor stack between the active layer and the reflector,
wherein the lower semiconductor stack comprises multiple semiconductor layers, and each of the multiple semiconductor layers has a refractive index ni, a thickness di and two sides each contacting adjacent layers to form two interfaces,
wherein each interface has a phase shift when the light ray travels through the two interfaces along a same direction, and
wherein, for one of the multiple semiconductor layers traveled through by the light ray, the thickness di satisfies at least one of the following conditions of:
(i) if the two phase shifts are the same, then 0.8*((2m−1)/2)*(λ/ni)≦di≦1.2*((2m−1)/2)*(λ/ni), where m is a natural number; and
(ii) if the two phase shifts are different, then 0.8*((2m−1)/4)*(λ/ni)≦di≦1.2*((2m−1)/4)*(λ/ni), where m is a natural number.
2. The light-emitting diode according to claim 1 , wherein the thickness di of the one of the multiple semiconductor layers is larger than one seventh of the peak wavelength λ in air.
3. The light-emitting diode according to claim 1 , wherein the lower semiconductor stack is made of p-type semiconductor material.
4. The light-emitting diode according to claim 1 , wherein the multiple semiconductor layers comprise a confining layer on the active layer, a cladding layer on the confining layer and a contact layer on the cladding layer.
5. The light-emitting diode according to claim 4 , wherein the two phase shifts of the two interfaces of the confining layer are the same.
6. The light-emitting diode according to claim 4 , wherein the confining layer contacting two adjacent layers, and the confining layer has a refractive index between the refractive indices of the two adjacent layers.
7. The light-emitting diode according to claim 4 , wherein the two phase shifts of the two interfaces of the cladding layer are different.
8. The light-emitting diode according to claim 4 , wherein the cladding layer contacting two adjacent layers, and the cladding layer has a refractive index smaller than the refractive indices of the two adjacent layers.
9. The light-emitting diode according to claim 4 , wherein the two phase shifts of the two interfaces of the contact layer are different.
10. The light-emitting diode according to claim 4 , wherein the contact layer contacting two adjacent layers, and the contact layer has a refractive index larger than the refractive indices of the two adjacent layers.
11. The light-emitting diode according to claim 1 , wherein each of the multiple semiconductor layers has a refractive index between 2.8 and 3.6.
12. The light-emitting diode according to claim 1 , wherein the peak wavelength λ in air is larger than 550 nm.
13. The light-emitting diode according to claim 1 , wherein the reflector comprises a metal layer contacting the lower semiconductor layer.
14. The light-emitting diode according to claim 1 , wherein the reflector comprises a dielectric layer contacting the lower semiconductor layer and the refractive index of the dielectric layer is smaller than that of the lower semiconductor stack.
15. The light-emitting diode according to claim 1 , wherein the reflector comprises a transparent conductive layer contacting the lower semiconductor layer and the refractive index of the transparent conductive layer is smaller than that of the lower semiconductor stack.
16. The light-emitting diode according to claim 1 , wherein a distance between the reflector and the active layer is between 250 nm and 1 μm.
17. The light-emitting diode according to claim 1 , further comprising a substrate and bonding layer adhering the substrate and the reflector.
18. The light-emitting diode according to claim 4 , further comprises a buffer layer between the contacting layer and the cladding layer.
19. The light-emitting diode according to claim 4 , wherein the contact layer comprises GaP.