Abstract:
A non-close-packed vertical junction photovoltaic device includes a substrate, a two-dimensional array of elongate nanostructures extending substantially perpendicularly from a surface of the substrate, and a thin film solar cell disposed over the nanostructures such that the thin film solar cell substantially conforms to the topography of the nanostructures. An average separation of nearest neighbor solar cell coated nanostructures is greater than zero and less than a vacuum wavelength of light corresponding to a band gap of absorption. The thin film solar cell may include an active region that conforms to the elongate nanostructures, a first electrode that conforms to a surface of the active region, and a second electrode. A separation of opposing outer surfaces of the first electrode extending along adjacent elongate nanostructures is greater than zero and less than the vacuum wavelength of the light corresponding to the band gap of the active region.
Abstract:
A III-nitride compound device which has a layer of AlInN (7) having a non-zero In content, for example acting as a current blocking layer, is described. The layer of AlInN (7) has at least aperture defined therein. The layer of AlInN (7) is grown with a small lattice-mismatch with an underlying layer, for example an underlying GaN layer, thus preventing added crystal strain in the device. By using optimised growth conditions the resistivity of the AlInN is made higher than 102 ohm·cm thus preventing current flow when used as a current blocking layer in a multilayer semiconductor device with layers having smaller resistivity. As a consequence, when the AlInN layer has an opening and is placed in a laser diode device, the resistance of the device is lower resulting in a device with better performance.
Abstract:
A semiconductor light-emitting device and a method of manufacture thereof A method of manufacturing a semiconductor light-emitting device comprises selectively etching a semiconductor layer structure (16) fabricated in a nitride materials system and including an aluminium-containing cladding region or an aluminium-containing optical guiding region (5). The etching step forms a mesa (17), and also exposes one or more portions of the aluminium-containing cladding region or the aluminium-containing optical guiding region (5). The or each exposed portion of the aluminium-containing cladding region or the aluminium-containing optical guiding region (5) Is then oxidised to form a current blocking layer (18) laterally adjacent to and extending laterally from the mesa. When an electrically conductive contact layer (11) is deposited, the current blocking layer (18) will prevent the contact layer (11) from making direct contact with the buffer layer (3).
Abstract:
A resonant tunneling device includes a first semiconductor material with an energy difference between valence and conduction bands of Eg1, and a second semiconductor material with an energy difference between valence and conduction bands of Eg2, wherein Eg1 and Eg2 are different from one another. The device further includes an energy selectively transmissive interface connecting the first and second semiconductor materials.
Abstract:
A method of growing a semiconductor layer structure comprises growing a first semiconductor layer and incorporating hydrogen into the first semiconductor layer. One or more further semiconductor layers are then grown over the first semiconductor layer to form a semiconductor layer structure. A selected portion of the first semiconductor layer is then annealed so as to change the electrical resistance of the selected portion of the first semiconductor layer. The electrical resistance of the one or more further semiconductor layers that have been grown over the first semiconductor layer is not significantly changed by the annealing step. The invention may be used, for example, to create a current aperture in a semiconductor layer within a semiconductor layer structure.
Abstract:
A method of growing a semiconductor layer structure comprises growing a first semiconductor layer and incorporating hydrogen into the first semiconductor layer. One or more further semiconductor layers are then grown over the first semiconductor layer to form a semiconductor layer structure. A selected portion of the first semiconductor layer is then annealed so as to change the electrical resistance of the selected portion of the first semiconductor layer. The electrical resistance of the one or more further semiconductor layers that have been grown over the first semiconductor layer is not significantly changed by the annealing step. The invention may be used, for example, to create a current aperture in a semiconductor layer within a semiconductor layer structure.
Abstract:
A resonant tunneling device includes a first semiconductor material with an energy difference between valence and conduction bands of Eg1, and a second semiconductor material with an energy difference between valence and conduction bands of Eg2, wherein Eg1 and Eg2 are different from one another. The device further includes an energy selectively transmissive interface connecting the first and second semiconductor materials.
Abstract:
A multi-junction photovoltaic structure which includes a first photovoltaic sub-cell having at least one junction, a second photovoltaic sub-cell having at least one junction and having a band gap smaller than a smallest band gap of the first photovoltaic sub-cell, and an interlayer that provides optical coupling between the first and second photovoltaic cells, wherein the interlayer has a physical thickness substantially similar or less than a vacuum wavelength of light corresponding to a smallest band gap of the second photovoltaic sub-cell.
Abstract:
A method of fabricating a continuous wave semiconductor laser diode in the (Al,Ga,In)N materials system comprises: growing, in sequence, a first cladding region (4), a first optical guiding region (5), an active region (6), a second optical guiding region (7) and a second cladding region (8). Each of the first cladding region (4), the first optical guiding region (5), the active region (6), the second optical guiding region (7) and the second cladding region (8) is deposited by molecular beam epitaxy.
Abstract:
A method of manufacturing a semiconductor light-emitting device is provided. The method includes the step of depositing an electrically conductive material on one or more selected portions of the surface of a semiconductor wafer including a substrate and a layer structure, the layer structure having at least a first semiconductor layer of a first conductivity type and a second semiconductor conductivity layer of a second conductivity type different from the first conductivity type, the first layer being between the second layer and the substrate, such that the electrically conductive material forms a contact to the first semiconductor layer. The method further includes the step of dicing the wafer to form a plurality of light-emitting devices, each light-emitting device having a respective part of the electrically conductive material.