Abstract: A semiconductor structure includes a GaAs or InP substrate, an InxGa1-xAs epitaxial layer grown on the substrate, where x is greater than about 0.01 and less than about 0.53, and a wider bandgap epitaxial layer grown as a cap layer on top of the InxGa1-xAs epitaxial layer.

Abstract: A semiconductor p-i-n photodiode having a substrate, an n layer coupled to the surface of said substrate, an i layer coupled to the surface of said n layer, and a carbon doped p layer coupled to the surface of said i layer.

Abstract: A monolithic integrated circuit device combines integrated heterostructure acoustic charge transport (HACT) devices and heterostructure insulated gate field effect transistor (HIGFET) devices in a single structure in which the HACT and HIGFET layers are grown in as a contiguous composite heterostructure.

Abstract: A heterojunction acoustic charge transport device (HACT) having a charge transport channel 39 which is sandwiched between upper and lower charge confinement layers, 14,20, has the charge transport channel 39 made of a Strained Layer Superlattice (SLS) comprising alternating deep-well semiconductor layers 40, that provide a deep quantum well depth, and strain relief layers 42 that provide strain relief to prevent dislocations from occurring due to lattice mismatches between the InGaAs layers within the channel 39 and the charge confinement layers 14,20, thereby allowing the overall thickness of the channel 39 to be at least as wide as conventional HACT devices that use a GaAs channel. The strain relief layers 42 may be narrowly sized to allow tunneling of electrons across the entire channel 39 thereby allowing the charge to move as a single group, or alternatively, widely sized to provide separate isolated channels thereby allowing the charge to move in separate groups.

Abstract: A heterojunction acoustic charge transport (HACT) device having a charge transport layer 16 surrounded by upper and lower charge confinement layers 14,30, respectively, and having a cap layer 36 at the outer surface, above the upper confinement layer 30, is provided with a P-N junction to minimize the effects of surface states. An intermediate layer 34 is disposed between the cap layer 36 and upper charge confinement layer 30. The upper confinement layer 30 and intermediate layer 34 are doped with opposite polarities to provide a P-N junction which creates a built-in electric field having sufficient strength to keep mobile charge carriers, transported by a SAW along the charge transport channel, from being trapped by or recombined with surface states at the external interface of the cap layer 36. Alternatively, the intermediate layer is not present and a cap layer 42 is doped to provide one side of the P-N junction.

Abstract: A one-dimensional or two-dimensional transmission mode spatial light modulator (SLM) includes one or more heterojunction acoustic charge transport (HACT) channels 18 with surrounding layers 16,20 vertically adjacent to a multiple quantum well (MQW) region 14, grown above a thick semiconductor substrate 10 thick enough to allow a surface acoustic wave (SAW) to propagate and transparent to the incident light 40. The SAW is injected by a transducer 24, charge is carried to and from the HACT channel 18 by electrodes 32,34,36, and light 40 is applied to a surface 44 perpendicular to the MQW region 14. Each charge packet 19 in the HACT channel 18 invokes an electric field 52 within the MQW region 14 which determines the optical absorption and index-of-refraction thereof, thereby determining the intensity and/or phase of each output light beam 45. Light modulation is achieved by modulating the amount of charge injected.

Abstract: A one-dimensional or two-dimensional transmission mode spatial light modulator (SLM) includes two different mediums, one medium being a semiconductor comprising one or more heterojunction acoustic charge transport (HACT) channels 28 with surrounding layers 26, 30 vertically adjacent to a multiple quantum well (MQW) region 22, and the other being a transparent piezoelectric insulating substrate 10 thick enough to allow a surface acoustic wave (SAW) 13 to propagate therein. The SAW 13 is launched in the substrate 10 by a transducer 12 and generates electric fields which propagate the charge along the HACT channel 28 in the semiconductor medium 18. Electrodes 32, 34, 36 carry charge to and from the HACT channel 28, and light 40 is applied to a surface 44 perpendicular to the MQW region 22.

Abstract: A simplified heterostructure charge transport device has a GaAs transport layer that is the top layer of the device, deposited on an (Al,Ga) As barrier layer for vertical confinement of charge packets. Confinement at the top surface is provided by pinning of the conduction band surface states.

Abstract: A novel heterostructure acoustic charge transport (HACT) device is capable of direct optical modulation. The device includes a transducer fabricated on a substrate structure that launches surface acoustic waves. A reflector is formed in the substrate structure at an end portion adjacent to the transducer for reflecting the surface acoustic waves. Also included is an electrode configured with the transport channel at an end thereof distal to the transducer for generating electrical signal equivalents of the propagating electrode charge. The device is characterized by a transport channel with an intrinsic vertical electrical potential such that electron-hole pairs created by incident electromagnetic radiation are separated from one another before recombination, with electrical charges therefrom provided to the surface acoustic waves.

Abstract: A novel heterojunction acoustic charge transport device includes a transducer fabricated on a GaAs/AlGaAs heterojunction material that launches surface acoustic waver (SAW) along a transport channel. The device is characterized by a photodiode configured adjacent to the channel on the substrate to receive a modulated optical beam. An electrical signal equivalent is provided to a Schottky electrode at the end of the transport channel modulating the charge propagated by the surface acoustic wave. The modulated signal is output at a distal end of the transport channel.

Abstract: An improved acoustic charge transport device having an acoustic wave passing through a piezoelectric semiconductor is improved by utilizing heterostructure Quantum-wells for confining charge packets.

Abstract: A novel heterojunction acoustic charge transport device (HACT) includes a modulation doped field effect transistor (MODFET) on the same substrate. The device is characterized by a sequence of epitaxial layers such that the MODFET is fabricated in a first portion of the uppermost layers while the HACT device is fabricated in an adjacent second portion using a partially overlapping subset of the lower layers after selected upper ones have been removed to form a single integrated electro-acoustic device.