Gallium nitride-based semiconductor element, optical device using the same, and image display apparatus using optical device
View Patent ↗A GaN-based semiconductor element which can suppress a leakage current generated during reverse bias application, an optical device using the same, and an image display apparatus using the optical device are provided. The GaN-based semiconductor element has a first GaN-based compound layer including an n-type conductive layer; a second GaN-based compound layer including a p-type conductive layer; and an active layer provided between the first GaN-based compound layer and the second GaN-based compound layer. In this GaN-based semiconductor element, the first GaN-based compound layer includes an underlayer having an n-type impurity concentration in the range of 3×10 18 to 3×10 19 /cm 3 , and when a reverse bias of 5 V is applied, a leakage current density, which is the density of a current flowing per unit area of the active layer, is 2×10 −5 A/cm 2 or less.
1. A gallium nitride-based semiconductor element comprising:
a first GaN-based compound layer comprising:
a first undoped GaN layer,
an n-type conductive first GaN-based compound semiconductor layer formed on the undoped GaN layer,
an underlayer formed directly on the n-type conductive first GaN-based compound semiconductor layer, and
a second undoped GaN layer formed directly on the underlayer;
an active layer formed on the second undoped GaN layer; and
a second GaN-based compound layer including a p-type conductive layer formed on the active layer such that the active layer is provided between the first GaN-based compound layer and the second GaN-based compound layer,
wherein the underlayer has an n-type impurity concentration in the range of 3×10 18 to 3×10 19 /cm 3 , and when a reverse bias of 5 V is applied, a leakage current density, which is the density of a current flowing per unit area of the active layer, is 2×10 −5 A/cm 2 or less.
2. The gallium nitride-based semiconductor element according to claim 1 , wherein the n-type impurity concentration of the underlayer is 4×10 18 /cm 3 or more, and the leakage current density is 8×10 −6 A/cm 2 or less.
3. The gallium nitride-based semiconductor element according to claim 1 , wherein the n-type impurity concentration of the underlayer is 8×10 18 /cm 3 or more, and the leakage current density is 1×10 −6 A/cm 2 or less.
4. The gallium nitride-based semiconductor element according to claim 1 , wherein the n-type impurity concentration of the underlayer is 1×10 19 /cm 3 or more, and the leakage current density is 6×10 −7 A/cm 2 or less.
5. The gallium nitride-based semiconductor element according to claim 1 , wherein the underlayer and the active layer each include a GaN-based compound containing In, the atomic composition ratio of In to the sum of In and Ga (In +Ga) in the GaN-based compound forming the underlayer is 0.005 or more and is lower than that of the GaN-based compound forming the active layer.
6. The gallium nitride-based semiconductor element according to claim 1 , wherein the underlayer has a thickness in the range of 5 nm to 5 μm.
7. The gallium nitride-based semiconductor element according to claim 1 , wherein the underlayer has a thickness in the range of 20 nm to 1 μm.
8. The gallium nitride-based semiconductor element according to claim 1 , wherein the second GaN-based compound layer includes a GaN layer doped with a p-type impurity and having a thickness of 100 nm or more.
9. The gallium nitride-based semiconductor element according to claim 1 , wherein the gallium nitride-based semiconductor element is a light-emitting element.
10. An optical device comprising:
a plurality of gallium nitride-based semiconductor elements, each of which is the gallium nitride-based semiconductor element according to claim 1 , arranged in a two-dimensional matrix,
wherein first electrodes of the gallium nitride-based semiconductor elements disposed along lines in a first direction are connected to common wires of the respective lines in the first direction, and
second electrodes of the gallium nitride-based semiconductor elements disposed along lines in a second direction are connected to common wires of the respective lines in the second direction.
11. An image display apparatus comprising:
a pixel portion including the optical device according to claim 10 ,
wherein the gallium nitride-based semiconductor elements are passive matrix driven.
12. The gallium nitride-based semiconductor element according to claim 1 , wherein the layers forming the first GaN-based compound layer and the second GaN-based compound layer are transparent to emission light wavelengths.
13. The gallium nitride-based semiconductor element according to claim 1 , wherein the n-type conductive first GaN-based compound semiconductor layer forms a contact with an n-type electrode.