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US 9,806,227 B2Granted
Ultraviolet light-emitting devices incorporating graded layers and compositional offsets
AssigneeCrystal IS, Inc.
InventorsCraig Moe, James R. Grandusky, Shawn R. Gibb, Leo J. Schowalter, Kosuke Sato, Tomohiro Morishita
Life of this patent
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Abstract
In various embodiments, light-emitting devices incorporate graded layers with compositional offsets at one or both end points of the graded layer to promote formation of two-dimensional carrier gases and polarization doping, thereby enhancing device performance.
Claims25
An ultraviolet (UV) light-emitting device comprising:
- a substrate having an AluGa1-uN top surface, wherein 0.4≦u≦1.0;
- an active, light-emitting device structure disposed over the substrate, the light-emitting device structure comprising a multiple-quantum well layer comprising a plurality of periods each comprising a strained AlxGa1-xN barrier and a strained AlyGa1-yN quantum well, x and y being different by an amount facilitating confinement of charge carriers in the multiple-quantum well layer;
- an electron blocking layer disposed over the multiple-quantum well layer, the electron blocking layer comprising AlvGa1-vN, wherein v>y and v>x;
- a graded AlzGa1-zN layer disposed over the electron blocking layer, a composition of the graded AlzGa1-zN layer being graded in Al concentration z such that the Al concentration z decreases in a direction away from the light-emitting device structure;
- a p-doped AlwGa1-wN cap layer disposed over the graded AlzGa1-zN layer, wherein 0≦w≦0.2;
- and
- a metallic contact disposed over the p-doped AlwGa1-wN cap layer and comprising at least one metal,
- wherein at an interface between the graded AlzGa1-zN layer and the electron blocking layer, the Al concentration z of the graded AlzGa1-zN layer is less than the Al concentration v of the electron blocking layer by an amount no less than 0.1 and by an amount no more than 0.55.
5 more elements
An ultraviolet (UV) light-emitting device comprising:
- a substrate having an AluGa1-uN top surface, wherein 0.4≦u≦1.0;
- an active, light-emitting device structure disposed over the substrate, the light-emitting device structure comprising a multiple-quantum well layer comprising a plurality of periods each comprising a strained AlxGa1-xN barrier and a strained AlyGa1-yN quantum well, x and y being different by an amount facilitating confinement of charge carriers in the multiple-quantum well layer;
- a graded AlzGa1-zN layer disposed over the multiple-quantum well layer, a composition of the graded AlzGa1-zN layer being graded in Al concentration z such that the Al concentration z decreases in a direction away from the light-emitting device structure;
- a p-doped AlwGa1-wN cap layer disposed over the graded AlzGa1-zN layer, wherein 0≦w≦0.2;
- and
- a metallic contact disposed over the p-doped AlwGa1-wN cap layer and comprising at least one metal,
- wherein at an interface between the graded AlzGa1-zN layer and the p-doped AlwGa1-wN cap layer, the Al concentration w of the p-doped AlwGa1-wN cap layer is less than the Al concentration z of the graded AlzGa1-zN layer by an amount no less than 0.1 and by an amount no more than 0.75.
4 more elements
Dependencies are inferred from the claim text.