Light emitting device

1. A light-emitting device, comprising:

a semiconductor stack;

a transparent substrate comprising a first material;

a bonding layer which bonds the semiconductor stack and the transparent substrate, wherein the bonding layer directly contacts the transparent substrate; and

a medium in the transparent substrate, the medium comprising a second material different from the first material, wherein the first material comprises sapphire while the second material comprises diamond, diamond-like carbon, or metal, or wherein the first material comprises glass while the second material comprises Bis(diethylammonium) tetrachlorocuprate (II) ([(CH 3 CH 2 ) 2 NH 2 ] 2 [CuCl 4 ]).

2. The light-emitting device as claimed in claim 1 , further comprising a reflective layer on the transparent substrate.

3. The light-emitting device as claimed in claim 1 , wherein the medium and the transparent substrate are devoid of any phosphor material.

4. The light-emitting device as claimed in claim 2 , further comprising a first electrode and a second electrode, wherein the first electrode and the second electrode are on an opposite side of the transparent substrate to the reflective layer wherein the second material comprises a conductor, a non-conductor, or a semiconductor.

5. The light-emitting device as claimed in claim 1 , wherein the metal is formed by metal ions implanted into sapphire.

6. The light-emitting device as claimed in claim 1 , wherein the medium comprising diamond, diamond-like carbon, or Bis(diethylammonium) tetrachlorocuprate (II) ([(CH 3 CH 2 ) 2 NH 2 ] 2 [CuCl 4 ]) is disposed into the transparent substrate at the same time during the process when the transparent substrate is formed.

7. The light-emitting device as claimed in claim 1 , further comprising rough surfaces on sidewalls of the transparent substrate wherein the bonding layer comprises a conductor or a non-conductor.

8. The light-emitting device as claimed in claim 1 , wherein the bonding layer is a non-conductor which comprises a polymer, an oxide, or a fluoride.

9. The light-emitting device as claimed in claim 1 , wherein the bonding layer comprises multiple layers of different materials.

10. The light-emitting device as claimed in claim 1 , wherein the bonding layer comprises a metal oxide, a metal with a thickness less than 500 Åor an alloy with a thickness less than 500 Å.

11. The light-emitting device as claimed in claim 1 , wherein the refractive index of the second material is between the refractive indices of the light-emitting stack and the first material.

12. The light-emitting device as claimed in claim 1 , wherein the refractive index of the second material is smaller than the refractive index of the first material.

13. The light-emitting device as claimed in claim 1 , wherein a maximum distance between two points of the shape of the medium is in the range of about 1 nm to 30 μm.