Semiconductor light-emitting element and method for manufacturing semiconductor light-emitting element
A semiconductor light-emitting element includes: an n-type clad layer of an n-type AlGaN-based semiconductor material; an active layer including a planarizing layer of an AlGaN-based semiconductor material provided on the n-type clad layer, a barrier layer of an AlGaN-based semiconductor material provided on the planarizing layer, and a well layer of an AlGaN-based semiconductor material provided on the barrier layer; and a p-type semiconductor layer provided on the active layer. The active layer emits deep ultraviolet light having a wavelength of 360 nm or shorter, and a ground level of a conduction band of the planarizing layer is lower than a ground level of a conduction band of the barrier layer and higher than a ground level of a conduction band of the well layer.
1. A method for manufacturing a semiconductor light-emitting element adapted to emit deep ultraviolet light having a wavelength of 360 nm or shorter, comprising:
forming an n-type clad layer of an n-type AlGaN-based semiconductor material;
forming a first barrier layer of an AlGaN-based semiconductor material on the n-type clad layer;
forming a planarizing layer of an AlGaN-based semiconductor material on and in contact with the first barrier layer;
forming a second barrier layer of an AlGaN-based semiconductor material on and in contact with the planarizing layer;
forming a well layer of an AlGaN-based semiconductor material on the second barrier layer;
forming an electron blocking layer of an AlGaN-based semiconductor material on and in direct contact with the well layer; and
forming a p-type semiconductor layer on the electron blocking layer, wherein
an AlN molar fraction of the n-type clad layer is 20% or higher,
an AlN molar fraction of the well layer is 10% or higher,
an AlN molar fraction of the planarizing layer is lower than an AlN molar fraction of each of the first barrier layer and the second barrier layer, and
a ground level of a conduction band of the planarizing layer is higher than a ground level of a conduction band of the well layer,
the ground level of the conduction band of the planarizing layer is lower than a ground level of a conduction band of the n-type clad layer,
a ground level of a conduction band of each of the first and second barrier layers is higher than the ground level of the conduction band of the n-type clad layer,
a ground level of a conduction band of the electron blocking layer is larger than the ground level of the conduction band of each of the first and second barrier layers, and
a difference in AlN molar fraction between the well layer and the planarizing layer is equal to 3%, or larger than 3% and smaller than 10%, or equal to 10%.
2. The method for manufacturing the semiconductor light-emitting element according to claim 1 , wherein a thickness of the planarizing layer in a direction of stack is smaller than a thickness of the well layer.
3. The method for manufacturing the semiconductor light-emitting element according to claim 1 , wherein the AlN molar fraction of the planarizing layer is higher than the AlN molar fraction of the well layer.
4. The method for manufacturing the semiconductor light-emitting element according to claim 1 , wherein a difference in the ground level of the conduction band between the planarizing layer and the well layer is equal to or larger than 2% of a light energy corresponding to a wavelength of light emitted from the well layer.
5. The method for manufacturing the semiconductor light-emitting element according to claim 1 , wherein
the forming of the first barrier layer or the second barrier layer comprises:
supplying a Group-III material and a Group-V material to grow an AlGaN-based semiconductor material layer; and
supplying a Group-V material for a duration not less than 6 seconds and not more than 30 seconds while a supply of the Group-III material is being stopped so as to stabilize the AlGaN-based semiconductor material layer.
6. A method for manufacturing a semiconductor light-emitting element adapted to emit deep ultraviolet light having a wavelength of 360 nm or shorter, comprising:
forming an n-type clad layer of an n-type AlGaN-based semiconductor material;
forming a first planarizing layer of an AlGaN-based semiconductor material on the n-type clad layer;
forming a first barrier layer of an AlGaN-based semiconductor material on and in contact with the first planarizing layer;
forming a second planarizing layer of an AlGaN-based semiconductor material on and in contact with the first barrier layer;
forming a second barrier layer of an AlGaN-based semiconductor material on and in contact with the second planarizing layer;
forming a well layer of an AlGaN-based semiconductor material on the second barrier layer;
forming an electron blocking layer of an AlGaN-based semiconductor material on and in direct contact with the well layer; and
forming a p-type semiconductor layer on the electron blocking layer, wherein
an AlN molar fraction of the n-type clad layer is 20% or higher,
an AlN molar fraction of the well layer is 10% or higher,
an AlN molar fraction of each of the first planarizing layer and the second planarizing layer is lower than an AlN molar fraction of each of the first barrier layer and the second barrier layer, and
a ground level of a conduction band of each of the first planarizing layer and the second planarizing layer is higher than a ground level of a conduction band of the well layer,
the ground level of the conduction band of each of the first planarizing layer and the second planarizing layer is lower than a ground level of a conduction band of the n-type clad layer,
a ground level of a conduction band of each of the first and second barrier layers is higher than the ground level of the conduction band of the n-type clad layer,
a ground level of a conduction band of the electron blocking layer is larger than the ground level of the conduction band of each of the first and second barrier layers, and
a difference in AlN molar fraction between the well layer and each of the first planarizing layer and the second planarizing layer is equal to 3%, or larger than 3% and smaller than 10%, or equal to 10%.
7. The method for manufacturing the semiconductor light-emitting element according to claim 6 , wherein
a thickness of each of the first planarizing layer and the second planarizing layer in a direction of stack is smaller than a thickness of the well layer.
8. The method for manufacturing the semiconductor light-emitting element according to claim 6 , wherein
the AlN molar fraction of each of the first planarizing layer and the second planarizing layer is higher than the AlN molar fraction of the well layer.
9. The method for manufacturing the semiconductor light-emitting element according to claim 1 , wherein a difference in the ground level of the conduction band between each of the first planarizing layer and the second planarizing layer and the well layer is equal to or larger than 2% of a light energy corresponding to a wavelength of light emitted from the well layer.
10. The method for manufacturing the semiconductor light-emitting element according to claim 6 , further comprising:
forming a further barrier layer of an AlGaN-based semiconductor material between the n-type clad layer and the first planarizing layer, wherein
the AlN molar fraction of each of the first planarizing layer and the second planarizing layer is lower than an AlN molar fraction of the further barrier layer, and
a ground level of a conduction band of the further barrier layer is higher than the ground level of the conduction band of the n-type clad layer.
11. The method for manufacturing the semiconductor light-emitting element according to claim 6 , wherein
the forming of the first barrier layer, the second barrier layer, or the further barrier layer comprises:
supplying a Group-III material and a Group-V material to grow an AlGaN-based semiconductor material layer; and
supplying a Group-V material for a duration not less than 6 seconds and not more than 30 seconds while a supply of the Group-III material is being stopped so as to stabilize the AlGaN-based semiconductor material layer.