Sharp Kabushiki Kaisha Corporation

University of Nottingham

Stewart Edward Hooper

Jonathan Heffernan

Valerie Bousquet

Tim Michael Smeeton

Jennifer Mary Barnes

Katherine L Johnson

Peter Neil Taylor

Alistair Henderson Kean

Edward Andrew Boardman

Geoffrey Duggan

Matthias Kauer

Rakesh Roshan

Katherine Louise Smith

Robin Mark Cole

Mathieu Xavier Sénès

Brendan Poole

Timothy David Bestwick

Michael Alan Schreuder

Charles Thomas Foxon

Alastair James Daniel Grundy

Tin Sung Cheng

The present application provides nitride semiconductor nanoparticles, for example nanocrystals, made from a new composition of matter in the form of a novel compound semiconductor family of the type group II-III-N, for example ZnGaN, ZnInN, ZnInGaN, ZnAlN, ZnAlGaN, ZnAlInN and ZnAlGaInN. This type of compound semiconductor nanocrystal is not previously known in the prior art. The invention also discloses II-N semiconductor nanocrystals, for example ZnN nanocrystals, which are a subgroup of the group II-III-N semiconductor nanocrystals. The composition and size of the new and novel II-III-N compound semiconductor nanocrystals can be controlled in order to tailor their band-gap and light emission properties. Efficient light emission in the ultraviolet-visible-infrared wavelength range is demonstrated. The products of this invention are useful as constituents of optoelectronic devices such as solar cells, light emitting diodes, laser diodes and as a light emitting phosphor material for LEDs and emissive EL displays.

II-III-N semiconductor nanoparticles and method of making same

A method of producing nitride nanoparticles comprises reacting at least one organometallic compound, for example an alkyl metal, with at least one source of nitrogen. The reaction may involve one or more liquid phase organometallic compounds, or may involve one or more liquid phase organometallic compounds dissolved in a solvent or solvent mixture. The reaction constituents may be heated to a desired reaction temperature (for example in the range 40&#xb0; C. to 300&#xb0; C.).

Method of synthesising nitride nanocrystals

A laser device is disclosed that provides at least an ultraviolet laser beam and preferably both an ultraviolet laser beam and a visible laser beam. The laser device includes a semiconductor laser device (e.g. a laser diode) to generate visible laser light which is coupled into a frequency doubling crystal taking the form of a single crystal thin film frequency-doubling waveguide structure. The single crystal thin film frequency-doubling waveguide converts a portion of the visible light emitted by the laser diode into ultraviolet light. Both visible and ultraviolet laser light is emitted from the waveguide. As an example, the single crystal thin film frequency-doubling frequency doubling waveguide includes a frequency doubling crystal region composed of &#x3b2;-BaBO(&#x3b2;-BBO), a cladding region composed of materials that are transparent or nearly transparent at the wavelength of the ultraviolet laser light beam and a supporting substrate composed of any material.

Ultraviolet laser

A method of manufacturing a semiconductor device comprises depositing a semiconductor layer over a semiconductor surface having at least one first region with a first (average surface lattice) parameter value and at least one second region having a second parameter value different from the first. The semiconductor layer is deposited to a thickness so self-organized islands form over both the first and second regions. The difference in the parameter value means the islands over the first region have a first average parameter value and the islands over the second region have a second average parameter value different from the first. A capping layer is deposited over islands and has a greater forbidden bandgap than the islands whereby the islands form quantum dots, which have different properties over the first and second regions due to difference(s) between the first and second region islands.

Semiconductor device and a method of manufacture thereof

A method of manufacturing a nitride semiconductor structure includes disposing a semiconductor substrate in a molecular beam epitaxy reactor; growing a wetting layer comprising AlInGa()As(0&#x2266;x+y&#x2266;1) or AlInGa()P(0&#x2266;x+y&#x2266;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.

Semiconductor structure and method of manufacture of same

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 (), a first optical guiding region (), an active region (), a second optical guiding region () and a second cladding region (). Each of the first cladding region (), the first optical guiding region (), the active region (), the second optical guiding region () and the second cladding region () is deposited by molecular beam epitaxy.

MBE growth of a semiconductor laser diode

A semiconductor light-emitting device fabricated in the (Al,Ga,In)N materials system has an active region for light emission () comprising InGaN quantum dots or InGaN quantum wires. An AlGaN layer () is provided on a substrate side of the active region. This increases the optical output of the light-emitting device. This increased optical output is believed to result from the AlGaN layer serving, in use, to promote the injection of carriers into the active region.

AlInGaN light-emitting device

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&#x2212;3, without the need for any post-growth step of activating the dopant atoms.

MBE growth of p-type nitride semiconductor materials

A method of MBE growth of a semiconductor layer structure comprises growing a first (Al,Ga)N layer (step) over a substrate at the first substrate temperature (T) using ammonia as the nitrogen precursor. The substrate is then cooled (step) to a second-substrate temperature (T) which is lower than the first substrate temperature. An (In,Ga)N quantum well structure is then grown (step) 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 (T) which is greater than the second substrate temperature (T). A second (Al,Ga)N layer is then grown over the (In,Ga)N quantum well structure (step).

MBE growth of a semiconductor layer structure

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

Semiconductor device and a method of manufacturing a semiconductor device

A method of manufacturing a semiconductor light-emitting device comprises selectively etching a semiconductor layer structure () fabricated in a nitride materials system and including an aluminum-containing cladding region or an aluminum-containing optical guiding region (). The etching step forms a mesa (), and also exposes one or more portions of the aluminum-containing cladding region or the aluminum-containing optical guiding region (). The or each exposed portion of the aluminum-containing cladding region or the aluminum-containing optical guiding region () is then oxidized to form a current blocking layer () laterally adjacent to and extending laterally from the mesa. When an electrically conductive contact layer () is deposited, the current blocking layer () will prevent the contact layer () from making direct contact with the buffer layer ().

Semiconductor light-emitting device and a method of manufacture thereof

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 10mbar, gallium is supplied at a beam equivalent pressure of at least 1 10mbar and aluminum is supplied at a beam equivalent pressure of at least 1 10mbar 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.

MBE growth of an algan layer or AlGaN multilayer structure

A method of manufacturing a nitride semiconductor device comprises the steps of: growing an InGaN (0&#x2266;x&#x2266;1) layer, and growing an aluminium-containing nitride semiconductor layer over the InGaN layer at a growth temperature of at least 500&#xb0; C. so as to form an electron gas region at an interface between the InGaN layer and the nitride semiconductor layer. The nitride semiconductor layer is then annealed at a temperature of at least 800&#xb0; C. The method of the invention can provide an electron gas having a sheet carrier density of 6&#xd7;10cmor 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 InGaN layer.

Growing community of inventors

Oxford, United Kingdom

Stewart Edward Hooper