Sharp Kabushiki Kaisha Corporation

Valerie Bousquet

Jonathan Heffernan

Stewart Edward Hooper

Katherine L Johnson

Jennifer Mary Barnes

Matthias Kauer

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 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 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.

Semiconductor light-emitting device, and a method of manufacture of a semiconductor device

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.

Semiconductor light-emitting device having an active region with aluminum-containing layers forming the lowermost and uppermost layer

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.

Method of growing a semiconductor layer

A method of fabricating the active region of a semiconductor light-emitting device, in which the active region comprises a plurality of barrier layers () with each pair of barrier layers being separated by a quantum well layer (), comprises annealing each barrier layer () separately. Each barrier layer () is annealed once it has been grown, and before a layer is grown over the barrier layer. A device grown by the method of the invention has a significantly higher optical power output than a device made by a convention fabrication process having a single annealing step.

Manufacture of a semiconductor device

The invention provides a method of growing an (In, Ga)N multiplayer structure by molecular beam epitaxy. Each GaN or InGaN layer in the multilayer structure is grown at a substrate temperature of at least 650&#xb0; C., and this provides improved material quality. Ammonia gas is used as the source of nitrogen for the growth process. Ammonia and gallium are supplied to the growth chamber at substantially constant rates, and the supply rate of indium to the growth chamber is varied to select the desired composition for the layer being grown. This allows the structure to be grown at a substantially constant growth rate. The substrate temperature is preferably kept constant during the growth process, to avoid the need to interrupt the growth process to vary the substrate temperature between the growth of one layer and the growth of another layer.

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Oxford, United Kingdom

Valerie Bousquet