At&t Bell Laboratories

American Telephone & Telegraph Co., At&t Bell Laboratories

American Telephone and Telegraph, Co.

Sergey Luryi

Ya-Hong Xie

John C Bean

Alexander Kastalsky

Federico Capasso

Gabriel L Miller

Rudolf F Kazarinov

Mark Richard Pinto

Thomas P Pearsall

Chun-Ting Liu

Vera B Gorfinkel

In accordance with the present invention, a silicon device fabricated on a (100) silicon substrate is provided with a (111) slant surface and an electrical contact comprising epitaxial low Schottky barrier silicide is formed on the (111) surface. For example, low resistance rare earth silicide contacts on V-groove surfaces are provided for the source and drain contacts of a field effect transistor. The resulting high quality contact permits downward scaling of the source and drain junction depths. As another example, rare earth silicide Schottky contacts are epitaxially grown on V-groove surfaces to provide low voltage rectifiers having both low power dissipation under forward bias and low reverse-bias leakage current.

Semiconductor devices using epitaxial silicides on (111) surfaces etched

Real space transfer (RST) semiconductor devices of novel geometry are disclosed. The devices are processed such that, at least in the active region of the devices, bulk semiconductor material is removed, and such that both the channel length L.sub.ch and the collector width W are defined lithographically. The channel length is defined by a trench etched through a highly conductive emitter contact layer. The trench is situated directly opposite the collector. Devices according to the invention can have relatively small parasitic capacitance, and therefore are potentially fast. A processing method that can be used to make devices of the novel geometry is also disclosed.

Article comprising a real space transfer semiconductor device, and

An article that comprises novel means for modulating the transparency of a semiconductor body in accordance with a modulating signal is disclosed. The body comprises one or more quantum wells (QWs), and the modulation mechanism comprises changing the free carrier distribution function in the QWs. An important feature of the inventive article is the use of (relatively long wavelength) inter-subband radiation (ISBR) to change the transparency of the body for (relatively short wavelength) inter-band radiation (IBR). In preferred embodiments the modulating signal is an electric field applied across the QWs, such that ISBR absorption can be tuned by means of the Stark effect. One embodiment of the invention makes it possible to rapidly modulate IBR, and another embodiment can form narrow (typically less than 10 ps) IBR pulses.

Article comprising means for modulating the optical transparency of a

A novel light emitting semiconductor device is disclosed. The device utilizes real space transfer (RST) of carriers, and comprises regions of opposite conductivity type separated by a barrier layer. The first region (termed the 'emitter') comprises at least two contacts. Application of appropriate bias between the two contacts and between the emitter and the second region results in injection of hot carriers into the second region, resulting in luminescence in the second region. The invention can be embodied in coherent as well as incoherent light sources. A preferred embodiment is a vertical cavity surface emitting laser. The device can serve as a novel logic element that has electrical inputs and an optical output, and provides a non-trivial logic function.

Light emitting device

Disclosed are novel fast semiconductor photodetector means that comprise a good asymmetric superlattice structure. Associated with the material of the structure is a relatively short minority carrier effective lifetime .tau..sub.e, typically .tau..sub.e &lt;10.sup.-9 sec. In response to a constant photon flux of appropriate wavelength the photodetector can have a substantially constant voltage output that is proportional to the photon flux for small values of flux, and that saturates at a value that is substantially proportional to .tau..sub.e.sup.-1 for relatively large values of flux. The novel photodetector means can be advantageously combined with a FET or bipolar transistor, and the combination can be part of an integrated circuit.

Staircase bandgap photodetector using recombination

Disclosed are articles and systems that comprise optically communicating logic elements. Exemplarily, a first logic element is a real space transfer logic element having two or more electrical input channels and an optical output channel, and a second logic element has two or more electrical input channels and an optical or an electrical output channel. Associated with at least one of the electrical input channels of the second element are means ('switching means') whose electrical state is responsive to an optical signal that impinges on the switching means (e.g., a photoconductor, phototransistor or photodiode). The elements are arranged such that the output signal of the first element impinges on the switching means, whereby the output of the second element is responsive to the output of the first element. In an exemplary embodiment the inventive article comprises massively parallel signal processing means comprising a multiplicity of optically communicating levels.

Articles and systems comprising optically communicating logic elements

In a vertical semiconductor laser, the top mirror is composed of alternating layers of lattice-mismatched semiconductors. Quantum reflections and other charge transport barriers for majority carriers at the interface, and hence electrical resistance and power dissipation, are reduced by choosing the lattice-mismatched semiconductor materials in such a manner as to align their band edges for majority carriers. On the other hand, the semiconductor materials are selected to supply relatively large refractive index differences, and hence relatively large optical reflections, at their interfaces. The lattice-mismatching may also produce vertical thread dislocations through the stack, which increase the electrical conductivity.

Vertical cavity semiconductor laser with lattice-mismatched mirror stack

Disclosed are a novel logic element (designated NORAND), and articles that comprise the element. Exemplarily, the NORAND element comprises three input terminals and an output terminal. If one of the input terminals is at logic 0 then the element functions as a logic NOR unit, and if the terminal is at logic 1 the element functions as a logic AND unit. The novel element thus makes possible reprogrammable and/or self-organizing logic circuits. The NORAND element can be realized with a single active semiconductor device, exemplarily a real space transfer (RST) device.

Logic element and article comprising the element

A vertical laser is typically formed by successive horizontal layers, epitaxially grown on a substrate, suitable for forming a bottom mirror, a bottom cladding layer, an active region, a top cladding layer, and a top mirror. In prior art, one of a pair of electrodes for enabling electrical pumping the laser--the 'top' electrode--is attached to the top surface of the top mirror, whereby undesirably large amounts of heat are generated because of the relatively high impedance of the top mirror. To reduce this heat generation, the laser is redesigned to enable the top electrode to make lateral contact with the top cladding layer, whereby the impedance and hence the power loss are reduced.

Vertical semiconductor laser with lateral electrode contact

Real space hot electron transfer devices using hot electron transfer between two conducting channels are described.

Real space electron transfer device using hot electron injection

A previously ignored property of a degenerate 2-dimensional gas of charge carriers in a quantum well (to be termed the quantum-capacitance effect) makes possible a novel class of transistors. In these devices the collector (a quantum well having high transverse conductance) is located between gate and emitter, with a barrier layer between emitter and collector, and a relatively thin barrier layer between collector and gate, and the chemical compositions and/or thicknesses of the various layers are chosen such that application of a voltage to the gate results, as a manifestation of the quantum-capacitance effect, in an induced charge in the emitter, whereby a current between emitter and collector can be controlled by means of a voltage applied to the gate. Transistors according to the invention potentially are very fast. Exemplarily the invention is embodied in a GaAs/AlGaAs heterostructure.

Transistor comprising a 2-dimensional carrier gas collector situated

A transistor device using an interdigitated gate and electrode surface structure to control thermionic emission over a potential barrier is described. Complementary logic structures comprising such transistors are discussed.

Transistor having voltage-controlled thermionic emission

Dislocation-free epitaxial layers on the surfaces of lattice mismatched single crystal substrates, such as germanium or gallium arsenide on silicon, can be grown provided the surfaces are suitably patterned, such as castellated or porous.

Dislocation-free epitaxial layer on a lattice-mismatched porous or

A semiconductor device comprising an epitaxially grown tin and Group IV compound semiconductor region on which at least one other semiconductor is grown lattice matched to the adjacent portion of the tin containing region. A large number of semiconductors may thus be grown.

Method of fabricating non-silicon materials on silicon substrate using

A photodetector, comprising a Ge.sub.x Si.sub.1-x superlattice region between two silicon cladding layers in which the Ge.sub.x Si.sub.1-x layers absorb light, is described.

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Bridgewater, NJ, United States of America

Sergey Luryi