Semiconductor light emitting devices with non-epitaxial upper cladding
View Patent ↗The AlGaN upper cladding layer of a nitride laser diode is replaced by a non-epitaxial layer, such as metallic silver. If chosen to have a relatively low refractive index value, the mode loss from absorption in the non-epitaxial cladding layer is acceptably small. If also chosen to have a relatively high work-function, the non-epitaxial layer forms an electrical contact to the nitride semiconductors. An indium-tin-oxide layer may also be employed with the non-epitaxial cladding layer.
1. A semiconductor light emitting device, comprising:
a substrate;
a crystalline semiconductor cladding layer formed over said substrate;
a confinement heterostructure formed over said crystalline semiconductor cladding layer;
an active region formed within said confinement heterostructure;
a phase matching layer formed over and in physical contact with said confinement heterostructure, said phase matching layer substantially optically transparent at the wavelength of operation of said semiconductor light emitting device;
a non-epitaxial cladding layer formed over and in physical contact with said phase matching layer, said non-epitaxial cladding layer having an electrical resistivity less than 1 ohm-cm; and
wherein said phase matching layer comprises a material selected from the group consisting of: indium tin oxide (ITO) and zinc oxide (ZnO).
2. The semiconductor light emitting device of claim 1 , wherein said confinement heterostructure comprises a material selected from the group consisting of: aluminum, indium, gallium.
3. The semiconductor light emitting device of claim 1 , wherein said non-epitaxial cladding layer is comprised of a metal.
4. The semiconductor light emitting device of claim 3 , wherein said non-epitaxial cladding layer is comprised of silver (Ag).
5. The semiconductor light emitting device of claim 1 , wherein said non-epitaxial cladding layer is both an upper cladding layer and a p-contact layer for the light emitting device.
6. The semiconductor light emitting device of claim 1 , wherein said non-epitaxial cladding layer is formed as a stripe over said confinement heterostructure to thereby provide a ridge waveguide.
7. A semiconductor light emitting device, comprising:
a substrate;
a crystalline semiconductor cladding layer formed over said substrate;
a confinement heterostructure formed over said crystalline semiconductor cladding layer;
an active region formed within said confinement heterostructure;
a phase matching layer formed over and in physical contact with said confinement heterostructure, said phase matching layer substantially optically transparent at the wavelength of operation of said semiconductor light emitting device;
a non-epitaxial cladding layer formed over and in physical contact with said phase matching layer, said non-epitaxial cladding layer having an electrical resistivity less than 1 ohm-cm; and
further comprising a dielectric layer, formed as a stripe over said confinement heterostructure and below said non-epitaxial cladding layer, and further wherein said non-epitaxial cladding layer is a periodic grating comprising discontinuous lateral ridge waveguide elements selectively formed over said dielectric layer.
8. The semiconductor light emitting device of claim 1 , wherein said non-epitaxial cladding layer forms an optical gain guide.
9. The semiconductor light emitting device of claim 1 , whereby said active region comprises indium gallium nitride (InGaN), and said semiconductor light emitting device emits light having a wavelength in the range of 350-550 nm.
10. The semiconductor light emitting device of claim 1 , wherein said semiconducting light emitting device is a semiconductor diode laser.
11. The semiconductor light emitting device of claim 1 , wherein said semiconducting light emitting device is a superluminescent diode.
12. The semiconductor light emitting device of claim 1 , wherein said non-epitaxial cladding layer is a composite comprising a conducting oxide and a metal.
13. The semiconductor light emitting device of claim 1 , whereby said active region comprises indium gallium aluminum nitride (InGaAlN), and said semiconductor light emitting device emits light having a wavelength in the range of 350-550 nm.
14. The semiconductor light emitting device of claim 13 , wherein said non-epitaxial cladding layer comprises a metal having a real component of its refractive index not exceeding 0.3 for wavelengths above 350 nm.
15. The semiconductor light emitting device of claim 1 , wherein said phase matching layer has an optical reflectivity exceeding 0.5 for light propagating from said confinement heterostructure.