Nitride semiconductor; light-emitting device, light-emitting diode, laser device and lamp using the semiconductor; and production methods thereof
A nitride semiconductor product including an n-type layer, a light-emitting layer, and a p-type layer which are formed of a nitride semiconductor and sequentially stacked on a substrate in the above order, the light-emitting layer having a quantum well structure in which a well layer is sandwiched by barrier layers having band gaps wider than the band gap of the well layer. Each barrier layer includes a barrier sublayer C which has been grown at a temperature higher than a growth temperature of the well layer, and a barrier sublayer E which has been grown at a temperature lower than a growth temperature of the barrier sublayer C. The barrier sublayer C is disposed closer to the substrate with respect to the barrier sublayer E.
1. A nitride semiconductor product comprising an n-type layer, a light-emitting layer, and a p-type layer which are formed of a nitride semiconductor and sequentially stacked on a substrate in the above order,
said light-emitting layer having a quantum well structure in which a well layer is sandwiched by barrier layers having band gaps wider than the band gap of the well layer,
wherein said barrier layers individually comprise a barrier sublayer C which has been grown at a temperature higher than a growth temperature of said well layer, and barrier sublayers A, B and E which have been grown at a temperature lower than a growth temperature of said barrier sublayer C, said barrier sublayers A, B, C, and E are stacked, in this order, said barrier sublayer A is grown by maintaining a temperature lower than a growth temperature of said barrier sublayer C, said barrier sublayer B is grown during elevating a temperature from the growth temperature of said barrier sublayer A to the growth temperature of said barrier sublayer C, the difference between the growth temperature of said barrier sublayer C and the growth temperature of said barrier sublayer E is 50°C. or more, said barrier sublayer E is grown by maintaining the lowered growth temperature after lowering the temperature.
2. A nitride semiconductor product comprising an n-type layer, a light-emitting layer, and a p-type layer which are formed of a nitride semiconductor and sequentially stacked on a substrate in the above order,
said light-emitting layer having a quantum well structure in which a well layer is sandwiched by barrier layers having band gaps wider than the band gap of the well layer,
wherein said barrier layers individually comprise a barrier sublayer C which has been grown at a temperature higher than a growth temperature of said well layer, and barrier sublayers D and E which have been grown at a temperature lower than a growth temperature of said barrier sublayer C, said barrier sublayers C, D and E are stacked, in this order, the difference between the growth temperature of said barrier sublayer C and the growth temperature of said barrier sublayer E is 50° C. or more, said barrier sublayer D is grown during lowering the temperature from the growth temperature of said barrier sublayer C to the growth temperature of said barrier sublayer E, and said barrier sublayer E is grown by maintaining the lowered growth temperature after lowering the temperature.
3. A nitride semiconductor product according to claim 1 or 2 , wherein the nitride semiconductor is represented by formula
In x Al y Ga 1-x-y N (0≦ x< 1, 0≦ y< 1,0≦ x +y< 1).
4. A nitride semiconductor product according to claim 1 or 2 , wherein the difference between the growth temperature of said barrier sublayer C and the growth temperature of said well layer is 50°C. or more.
5. A nitride semiconductor product according to claim 1 wherein the difference between the growth temperature of said barrier sublayer C and the growth temperature of said barrier sublayer A is 50°C. or more.
6. A nitride semiconductor product according to claim 1 or 2 , wherein the growth temperature of said well layer falls within a range of 600°C. to 1,000°C.
7. A nitride semiconductor product according to claim 3 , wherein said well layer comprises GaInN.
8. A nitride semiconductor product according to claim 3 , wherein said barrier layer comprises GamiN or GaN.
9. A nitride semiconductor product according to claim 1 or 2 , wherein at least one layer selected from said well layer and said barrier layer contains an n- type dopant.
10. A nitride semiconductor product according to claim 9 , wherein said n-type dopant is Si.
11. A nitride semiconductor product according to claim 9 , wherein said n-type dopant is Ge.
12. A nitride semiconductor product according to claim 9 , wherein a concentration of said n-type dopant in the layer containing said n-type dopant varies periodically.
13. A nitride semiconductor product according to claim 12 , wherein a layer with a higher concentration of said n-type dopant is not thicker than a layer with a lower concentration of said n-type dopant, in the layer containing said n-type dopant.
14. A nitride semiconductor product according to claim 9 , wherein the layer containing said n-type dopant has an n-type dopant concentration of 1× 10 16 to 5× 10 19 cm −3 .
15. A nitride semiconductor light-emitting device comprising a nitride semiconductor product according to claim 1 or 2 , a negative electrode provided on an n-type layer of said nitride semiconductor product and a positive electrode provided on a p-type layer of said nitride semiconductor product.
16. A light-emitting diode comprising a nitride semiconductor product according to claim 1 or 2 .
17. A laser device comprising a nitride semiconductor product according to claim 1 or 2 .
18. A lamp comprising a nitride semiconductor product according to claim 1 or 2 .
19. A method for producing a nitride semiconductor product, said method comprising sequentially stacking on a substrate a nitride semiconductor n-type layer, a nitride semiconductor light-emitting layer of a quantum well structure, and a nitride semiconductor p-type layer, thereby producing a nitride semiconductor product having a quantum well structure, wherein said method comprises
growing a well layer;
subsequently, elevating a growth temperature;
growing a barrier layer of the quantum well structure at the elevated temperature, which is higher than a growth temperature of the well layer by 50°C. or more;
subsequently, lowering the growth temperature again by 50°C. or more; and
further growing the barrier layer at the lowered temperature.
20. A method for producing a nitride semiconductor product according to claim 19 , which further comprises growing said barrier layer before elevating the growth temperature.
21. A method for producing a nitride semiconductor product according to claim 19 , wherein growing of said barrier layer is performed in at least one step of elevating the growth temperature and lowering the growth temperature.
22. A method for producing a nitride semiconductor product according to claim 19 , wherein said barrier layer contains an n-type dopant.
23. A method for producing a nitride semiconductor light-emitting device, said method comprising
a step of producing a nitride semiconductor product comprising an n-type layer, a light-emitting layer and a p-type layer by the method for producing a nitride semiconductor product according to claim 19 , a step of removing a portion of a light-emitting layer and a p-type layer of the nitride semiconductor product , thereby exposing an n-type layer,
a step of providing a negative electrode on the exposed n-type layer, and
a step of providing a positive electrode on the p-type layer.
24. A method for producing a light-emitting diode, comprising a step of providing a lead to a nitride semiconductor light-emitting device produced by the method according to claim 23 .
25. A method for producing a laser device, comprising a step of providing a lead to a nitride semiconductor light-emitting device produced by the method according to claim 23 .
26. A method for producing a lamp, comprising a step of providing a cover containing a phosphor to a nitride semiconductor light-emitting device produced by the method according to claim 23 .