Abstract: A method comprises forming elongate structures (5) on a first substrate (3), such that the material composition of each elongate structure (7) varies along its length so as to define first and second physically different sections in the elongate structures. First and second physically different devices (1,2) are then defined in the elongate structures. Alternatively, the first and second physically different sections may be defined in the elongate structures after they have been fabricated. The elongate structures may be encapsulated and transferred to a second substrate (7). The invention provides an improved method for the formation of a circuit structure that requires first and second physically different devices (1,2) to be provided on a common substrate. In particular, only one transfer step is necessary.

Abstract: A light emitting diode device which includes at least one light emitting diode, a heat-sink chassis having a surface upon which the at least one light emitting diode is mounted, and a waveguide having one end coupled to the at least one light emitting diode for receiving light therefrom. The waveguide has another end which includes a light extraction and redistribution region, and the waveguide is configured to guide light received from the at least one light emitting diode away from the heat-sink chassis and towards the light extraction and redistribution region. The light extraction and redistribution region is configured to extract and redistribute the light from the waveguide.

Abstract: A method of growing a thin film comprises growing a thin film by conformally forming at least one layer over a substrate having structures extending from a surface of the substrate, whereby the or each layer is formed over the surface of the substrate and over the structures extending from the surface. The thickness of the conformal layer, or the sum of the thicknesses of the conformal layers, is at least half the average spacing of the structures, and; at least one of the height of the structures, the average spacing of the structures and the size of the smallest dimension of the structures is set so as to provide an enhanced growth rate for the or each conformal layer (compared to the growth rate over a planar substrate).

Abstract: A method of manufacturing a nitride semiconductor structure includes disposing a semiconductor substrate in a molecular beam epitaxy reactor; growing a wetting layer comprising AlxInyGa(1?(x+y))As(0?x+y?1) or AlxInyGa(1?(x+y))P(0?x+y?1) on the substrate; in-situ annealing the wetting layer; growing a first AlGaInN layer on the wetting layer using plasma activated nitrogen as the source of nitrogen with an additional flux of phosphorous or arsenic; and growing a second AlGaInN layer on the first AlGaInN layer using ammonia as a source of nitrogen.

Abstract: A method includes forming elongate structures (5) on a first substrate (3), such that the material composition of each elongate structure (7) varies along its length so as to define first and second physically different sections in the elongate structures. First and second physically different devices (1, 2) are then defined in the elongate structures. Alternatively, the first and second physically different sections may be defined in the elongate structures after they have been fabricated. The elongate structures may be encapsulated and transferred to a second substrate (7). The invention provides an improved method for the formation of a circuit structure that requires first and second physically different devices (1,2) to be provided on a common substrate. In particular, only one transfer step is necessary.

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 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: An illumination system comprises at least two light sources (101,102,103) having different emission spectra to one another; a detection circuit (131,132,133) for sensing a light intensity using at least one of the light sources as a photosensor; and driving means (161,162,163) for driving the light source in dependence on the sensed spectral distribution of light. The emission spectrum of a light source with the smallest bandgap overlaps the emission spectrum of a light source with the second-smallest bandgap. The illumination system is possible to measure the intensity of light emitted by the light source with the smallest bandgap by putting the light source with the second-smallest bandgap in detection mode. The illumination system may also sense the spectral distribution of ambient light, to allow the output from the illumination system to be adjusted in dependence on the ambient light.

Abstract: A method of manufacturing a nitride semiconductor structure includes disposing a semiconductor substrate in a molecular beam epitaxy reactor; growing a wetting layer comprising AlxInyGa(1?(x/y))As(0?x+y?1) or AlxInyGa(1?(x/y))P(0?x+y?1) on the substrate; in-situ annealing the wetting layer; growing a first AlGaInN layer on the wetting layer using plasma activated nitrogen as the source of nitrogen with an additional flux of phosphorous or arsenic; and growing a second AlGaInN layer on the first AlGaInN layer using ammonia as a source of nitrogen.

Abstract: A method of encapsulating low dimensional structures comprises forming a first group (3a) of low dimensional structures (1) and a second group (3b) of low dimensional structures (1) on a first substrate. The first group (3a) of low dimensional structures (1) and the second group (3b) of low dimensional structures (1) are encapsulated in a matrix (5), with the first group (3a) of low dimensional structures (1) being encapsulated separately from the second group (3b) of low dimensional structures (1). After encapsulation, the first group (3a) of low dimensional structures (1) may be separated from the second group (3b) of low dimensional structures (1). Each group may then be processed, for example by transfer to a second substrate (7). The number of low dimensional structures in a group, and the aspect ratio of a group is defined when the low dimensional structures are formed, and can therefore be controlled more accurately than in a conventional method in which groups are defined using a patterning technique.

Abstract: A method of growing a p-type nitride semiconductor material by molecular beam epitaxy (MBE) uses bis(cyclopentadienyl)magnesium (Cp2Mg) as the source of magnesium dopant atoms. Ammonia gas is used as the nitrogen precursor for the MBE growth process. To grow p-type GaN, for example, by the method of the invention, gallium, ammonia and Cp2Mg are supplied to an MBE growth chamber; to grow p-type AlGaN, aluminum is additionally supplied to the growth chamber. The growth process of the invention produces a p-type carrier concentration, as measured by room temperature Hall effect measurements, of up to 2 1017 cm?3, without the need for any post-growth step of activating the dopant atoms.

Abstract: A method of MBE growth of a semiconductor layer structure comprises growing a first (Al,Ga)N layer (step 13) over a substrate at the first substrate temperature (T1) using ammonia as the nitrogen precursor. The substrate is then cooled (step 14) to a second-substrate temperature (T2) which is lower than the first substrate temperature. An (In,Ga)N quantum well structure is then grown (step 15) over the first (Al,Ga)N layer by MBE using ammonia as the nitrogen precursor. The supply of ammonia to the substrate is maintained continuously during the first growth step, the cooling step, and the second growth step. After completion of the growth of the (In,Ga)N quantum well structure, the substrate may be heated to a third temperature (T3) which is greater than the second substrate temperature (T2). A second (Al,Ga)N layer is then grown over the (In,Ga)N quantum well structure (step 17).

Abstract: A semiconductor device comprises an active region (4), a cladding layer (5,7), and a saturable absorbing layer (6) disposed within the cladding layer. The saturable absorbing layer comprises at least one portion (11a) that is absorbing for light emitted by the active region and comprises at least portion (11b) that is not absorbing for light emitted by the active region. The fabrication method of the invention enables the non-absorbing portion(s) (11b) of the saturable absorbing layer (6) to produced after the device structure has been fabricated. This allows the degree of overlap between the non-absorbing portion(s) (11b) of the saturable absorbing layer (6) and the optical mode of the laser to be altered after the device has been grown.

Abstract: A method comprises forming elongate structures (5) on a first substrate (3), such that the material composition of each elongate structure (7) varies along its length so as to define first and second physically different sections in the elongate structures. First and second physically different devices (1,2) are then defined in the elongate structures. Alternatively, the first and second physically different sections may be defined in the elongate structures after they have been fabricated. The elongate structures may be encapsulated and transferred to a second substrate (7). The invention provides an improved method for the formation of a circuit structure that requires first and second physically different devices (1,2) to be provided on a common substrate. In particular, only one transfer step is necessary.

Abstract: A method of fabricating a device structure, comprises: forming an insulating layer (3b) over a first set of devices disposed over a substrate (3); forming one or more vias in the insulating layer; disposing a second set of devices (6) over the insulating layer, wherein devices of the second set comprise respective electrical contacts (6a) and are disposed over the insulating layer (3b) such that a side on which a contact (6a) can be accessed faces the substrate (3); and forming one or more electrical contacts between the first set of devices and the second set of devices (6) through the via(s). The second set of devices and at least one via are positioned such that one or more of the vias lies at least partially within the footprint of two devices, each belonging to a different device layer.

Abstract: 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 aluminum-containing cladding region or an aluminum-containing optical guiding region (5). The etching step forms a mesa (17), and also exposes one or more portions of the aluminum-containing cladding region or the aluminum-containing optical guiding region (5). The or each exposed portion of the aluminum-containing cladding region or the aluminum-containing optical guiding region (5) is then oxidized 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 method of growing an AlGaN semiconductor layer structure by Molecular Beam Epitaxy comprises supplying ammonia, gallium and aluminum to a growth chamber thereby to grow a first (Al,Ga)N layer by MBE over a substrate disposed in the growth chamber. The first (Al,Ga)N layer has a non-zero aluminum mole fraction. Ammonia is supplied at a beam equivalent pressure of at least 1 10?4 mbar, gallium is supplied at a beam equivalent pressure of at least 1 10?8 mbar and aluminum is supplied at a beam equivalent pressure of at least 1 10?8 mbar during the growth step. Once the first (Al,Ga)N layer has been grown, varying the supply rate of gallium and/or aluminum enables a second (Al,Ga)N layer, having a different aluminum mole fraction from the first (Al,Ga)N layer to be grown by MBE over the first (Al,Ga)N layer. This process may be repeated to grown an (Al,Ga)N multilayer structure.

Abstract: A method of manufacturing a nitride semiconductor device comprises the steps of: growing an InxGa1-xN (0?x?1) layer, and growing an aluminium-containing nitride semiconductor layer over the InxGa1-xN layer at a growth temperature of at least 500° C. so as to form an electron gas region at an interface between the InxGa1-xN layer and the nitride semiconductor layer. The nitride semiconductor layer is then annealed at a temperature of at least 800° C. The method of the invention can provide an electron gas having a sheet carrier density of 6×1013cm?2 or greater. An electron gas with such a high sheet carrier concentration can be obtained with an aluminium-containing nitride semiconductor layer having a relatively low aluminium concentration, such as an aluminium mole fraction of 0.3 or below, and without the need to dope the aluminium-containing nitride semiconductor layer or the InxGa1-xN layer.

Abstract: A semiconductor light-emitting device fabricated in a nitride material system has an active region disposed over a substrate. The active region comprises a first aluminium-containing layer forming the lowermost layer of the active region, a second aluminium-containing layer forming the uppermost layer of the active region, and at least one InGaN quantum well layer disposed between the first aluminium-containing layer and the second aluminum-containing layer. The aluminium-containing layers provide improved carrier confinement in the active region, and so increase the output optical power of the device.

Abstract: A method of growing a p-type nitride semiconductor material having magnesium as a p-type dopant by molecular beam epitaxy (MBE), comprises supplying ammonia gas, gallium and magnesium to an MBE growth chamber containing a substrate so as to grow a p-type nitride semiconductor material over the substrate. Magnesium is supplied to the growth chamber at a beam equivalent pressure of at least 1 10-9 mbar, and preferably in the range from 1 10-9 mbar to 1 10-7 mbar during the growth process. This provides p-type GaN that has a high concentration of free charge carriers and eliminates the need to activate the magnesium dopant atoms by annealing or irradiating the material.