Light-emitting diode and method for manufacturing tunnel junction layer

1. A light-emitting diode comprising:

a first light-emitting part including a first p-type layer, a first n-type layer, and a first active layer, the first p-type layer containing a compound semiconductor and p-type impurities, the first n-type layer containing a compound semiconductor and n-type impurities, the first active layer containing a compound semiconductor and being sandwiched between the first p-type layer and the first n-type layer;

a second light-emitting part including a second p-type layer, a second n-type layer, and a second active layer, the second p-type layer containing a compound semiconductor and p-type impurities, the second n-type layer containing a compound semiconductor and n-type impurities, the second active layer containing a compound semiconductor and being sandwiched between the second p-type layer and the second n-type layer, the second light-emitting part emitting light of the same wavelength as the first light-emitting part; and

a tunnel junction part including a third p-type layer and a third n-type layer, the third p-type layer facing the first p-type layer and containing Al x Ga 1-x As (0≤x≤0.3) and p-type impurities, the third n-type layer facing the second n-type layer and containing (Al x Ga 1-x ) y In 1-y P (0≤x≤0.2, 0.4≤y≤0.6) and n-type impurities, the tunnel junction part being sandwiched between the first light-emitting part and the second light-emitting part, the third p-type layer and the third n-type layer forming a tunnel junction.

2. The light-emitting diode according to claim 1 , wherein the tunnel junction part further includes a highly n-type impurities-doped layer at a boundary between the third p-type layer and the third n-type layer, the highly n-type impurities-doped layer containing n-type impurities at a higher concentration than the third n-type layer.

3. The light-emitting diode according to claim 2 , wherein the highly n-type impurities-doped layer is thinner than the third n-type layer and the third p-type layer.

4. The light-emitting diode according to claim 2 , wherein a concentration of the n-type impurities in the highly n-type impurities-doped layer is not less than 1×10 20 cm −3 and not more than 1×10 21 cm −3 .

5. The light-emitting diode according to claim 1 , wherein a concentration of the n-type impurities in the third n-type layer is higher at a side facing the third p-type layer than at a side facing the second n-type layer.

6. The light-emitting diode according to claim 1 , wherein a concentration of the p-type impurities in the third p-type layer is higher at a side facing the third n-type layer than at a side facing the first p-type layer.

7. The light-emitting diode according to claim 1 , wherein both of the first active layer and the second active layer have a single- or multi-quantum well structure including a well layer and a barrier layer,

the well layer is composed of (Al x Ga 1-x ) y In 1-y As z P 1-z (0≤x≤0.2, 0.7≤y≤1.0, 0.7≤z≤1.0), and

the barrier layer is composed of Al x Ga 1-x As z P 1-z (0≤x≤0.3, 0.7≤z≤1.0).

8. The light-emitting diode according to claim 1 , wherein each of the first p-type layer, the second p-type layer and the third p-type layer contains C as p-type impurities, and

each of the first n-type layer, the second n-type layer and the third n-type layer contains Te as n-type impurities.

9. A light-emitting diode comprising:

a first light-emitting part including a first p-type layer, a first n-type layer, and a first active layer, the first p-type layer containing Al, Ga, As and p-type impurities, the first n-type layer containing Al, Ga, As and n-type impurities, the first active layer containing a group III-V semiconductor and being sandwiched between the first p-type layer and the first n-type layer;

a second light-emitting part including a second p-type layer, a second n-type layer, and a second active layer, the second p-type layer containing Al, Ga, As and p-type impurities, the second n-type layer containing Al, Ga, As and n-type impurities, the second active layer containing a group III-V semiconductor and being sandwiched between the second p-type layer and the second n-type layer, the second light-emitting part emitting light of the same wavelength as the first light-emitting part; and

a tunnel junction part including a third p-type layer and a third n-type layer, the third p-type layer facing the first p-type layer and containing Ga, As and p-type impurities, the third n-type layer facing the second n-type layer and containing Ga, In, P and n-type impurities, the tunnel junction part being sandwiched between the first light-emitting part and the second light-emitting part, the third p-type layer and the third n-type layer forming a tunnel junction.

10. The light-emitting diode according to claim 9 , wherein the third n-type layer has a larger band gap than the third p-type layer.

11. The light-emitting diode according to claim 9 , wherein the first p-type layer and the second n-type layer have a common composition except for contained impurities.

12. The light-emitting diode according to claim 9 , wherein each of the third p-type layer and the third n-type layer is composed of a direct band gap semiconductor.

13. The light-emitting diode according to claim 9 , wherein a concentration of the n-type impurities in the third n-type layer is not less than 1×10 20 cm −3 and not more than 1×10 21 cm −3 .