Multiple quantum well structure and light emitting diodes

1. A Group-III-nitride-based multiple quantum well structure having at least one quantum well, comprising:

a first protection layer;

a first intermediate layer over the first protection layer;

a well layer over the first intermediate layer with a thickness of 0-5 nm;

a second intermediate layer over the quantum well layer;

a second protection layer based on Group-III nitrides over the second intermediate layer; and

a barrier layer over the second protection layer;

wherein:

growth temperatures of the first protection layer and the second protection layer are not lower than that of the quantum well layer, and not higher than that of the quantum well layer temperature by 100° C.; and

a band gap of the first intermediate layer is not larger than that of the first protection layer and not less than that of the well layer, and has a gradual decrease during growth, and a band gap of the second intermediate layer is not larger than that of the second protection layer and not less than that of the well layer, and has a gradual increase during growth.

2. The multiple quantum well structure of claim 1 , wherein:

at least one of the first protection layer or the second protection layer is made of Al a In b Ga 1-a-b N; and

0≤a≤1, 0≤b≤1, 0≤a+b≤1.

3. The multiple quantum well structure of claim 1 , wherein:

thicknesses of the first protection layer and the second protection layer are represented with n and m, respectively; and

0<n≤5 nm, 0<m≤5 nm.

4. The multiple quantum well structure of claim 1 , wherein: a band gap of the first protection layer is not less than a band gap of the first intermediate layer material.

5. The multiple quantum well structure of claim 1 , wherein: a band gap of the second protection layer is not less than a band gap of the second intermediate layer.

6. The multiple quantum well structure of claim 1 , wherein:

at least one of the first intermediate layer or the second intermediate layer is made of Al p In q Ga 1-p-q N; and

0≤p≤1, 0≤q≤1, 0≤p+q≤1.

7. The multiple quantum well structure of claim 1 , wherein:

thicknesses of the first intermediate layer and the second intermediate layer are represented with i and j, respectively;

0≤i≤5 nm, 0≤j≤5 nm; and

i and j are not 0 at a same time.

8. The multiple quantum well structure of claim 1 , wherein: during growth of the first intermediate layer, a growth temperature is reduced from a growth temperature of the first protection layer to a growth temperature of the well layer through a monotonic decrease.

9. The multiple quantum well structure of claim 1 , wherein: during growth of the second intermediate layer, a growth temperature is increased from a growth temperature of the well layer to a growth temperature of the second protection layer through a monotonic increase.

10. The multiple quantum well structure of claim 1 , wherein: the well layer is made of Al x In y Ga 1-x-y N, and 0≤x≤1, 0≤y≤1, 0≤x+y≤1.

11. The multiple quantum well structure of claim 1 , wherein: the barrier layer is made of Al c In d Ga 1-c-d N, and 0≤c≤1, 0≤d≤1, 0≤c+d≤1.

12. The multiple-quantum well structure of claim 1 , wherein: the barrier layer has a thickness of 0-50 nm.

13. The multiple quantum well structure of claim 1 , wherein: the barrier layer is fully doped or partially doped with a doping concentration not more than 5×10 19 cm −3 .

14. A light-emitting diode (LED), comprising:

an N-type conductive layer;

a P-type conductive layer; and

a light emitting layer between the N-type conductive layer and the P-type conductive layer, wherein the light emitting layer includes:

a Group-III-nitride-based multiple quantum well structure having at least one quantum well, comprising:

a first protection layer;

a first intermediate layer over the first protection layer;

a well layer over the first intermediate layer with a thickness of 0-5 nm;

a second intermediate layer over the quantum well layer;

a second protection layer based on Group-III nitrides over the second intermediate layer; and

a barrier layer over the second protection layer;

wherein:

growth temperatures of the first protection layer and the second protection layer are not lower than that of the quantum well layer, and not higher than that of the quantum well layer temperature by 100° C.; and

a band gap of the first intermediate layer is not larger than that of the first protection layer and not less than that of the well layer, and has a gradual decrease during growth, and a band gap of the second intermediate layer is not larger than that of the second protection layer and not less than that of the well layer, and has a gradual increase during growth.

15. The LED of claim 14 , wherein:

at least one of the first protection layer or the second protection layer is made of Al a In b Ga 1-a-b N; and

0≤a≤1, 0≤b≤1, 0≤a+b≤1.

16. A method of growing a Group-III-nitride-based multiple quantum well structure having at least one quantum well, the structure comprising:

a first protection layer;

a first intermediate layer over the first protection layer;

a well layer over the first intermediate layer;

a second intermediate layer over the quantum wall layer;

a second protection layer based on Group-ill nitrides over the second intermediate layer; and

a barrier layer over the second protection layer, wherein the method comprises:

growing the first protection layer at a first temperature; growing the first intermediate layer at monotonically decreasing temperatures from the first temperature to a second temperature; and

growing the well layer at the second temperature;

wherein, growing the second intermediate layer with monotonically increasing temperatures form the second temperature to a third temperature; and growing the second protection layer at the third temperature; wherein: a band gap of the first intermediate layer is not larger than band gap of the first protection layer and not less than a band gap of the well layer, the method further comprising gradually decreasing the band gap of the first intermediate layer during growth; and a band gap of the second intermediate layer is not larger than a band gap of the second protection layer and not less than a band gap of the well layer, the method further comprising gradually increasing the hand gap of the second intermediate layer during growth.