Abstract: A double heterostructure light emitting semiconductor device is described wherein a narrow bandgap active region is sandwiched between two wider bandgap cladding layers, one of which contains a p-n homojunction. The purpose is to separate the p-n junction from the active region and, thus, to have the active region bounded by two isotype (p-p or n-n) heterojunctions. This configuration significantly reduces nonradiative interface recombination current which occurs principally at the anisotype (p-n) heterojunction in a standard double heterostructure.

Abstract: Surface recombination current in GaAs devices is reduced by means of a semi-insulating, oxygen, iron or chromium doped monocrystalline layer of AlGaAs grown by MBE. The AlGaAs layer is grown on a GaAs body and is then masked. Diffusion of suitable impurities through a window in the mask converts the exposed portions of the AlGaAs layer to low resistivity and modifies the conductivity of the underlying zone of the GaAs body. The peripheral portions of the AlGaAs layer, however, remain semi-insulating and are effective to reduce the surface recombination velocity - diffusion length product by more than an order of magnitude.

Abstract: The tracking problems of prior art optical monitoring (e.g., feedback stabilization) schemes are substantially alleviated by positioning a photodiode (PD 130) directly in the light path of the optical source (100) to be stabilized. The active (light-absorbing) layer (104) of the PD samples (absorbs) only a small portion of the light beam (140) emanating from the source and converts that portion to a photocurrent used in a feedback loop (120, 101) to control the excitation supplied to the source. The remaining, major portion (140') of the beam is transmitted unabsorbed through the PD active layer to utilization means (e.g., through an optical fiber 108 to a remote receiver). Advantageously, in one embodiment the PD is a double heterostructure (DH) in which the photocurrent is linearly related to the beam intensity. The use of discrete or integrated lens means (110, 110', 164, 166) to enhance coupling from the source to PD is described.

Abstract: An oxide layer (16') is formed on a GaAs body (14) by epitaxially growing a layer (12) of Al.sub.x Ga.sub.1-x As layer on a major surface (18) of the body and then thermally oxidizing the Al.sub.x Ga.sub.1-x As layer for a time period effective to convert it to an oxide. The oxidizing process is essentially self-terminating at the major surface 18. The application of this process to the fabrication of MOS capacitors and IGFETs is described.

Abstract: A light transducer (10) is described in which a semi-insulating, single crystal body (12) of light-absorbing semiconductor material has a pair of spaced-apart epitaxial zones (14, 16) of opposite conductivity type integrally and electrically coupled to a surface (18) of the body. The zones, which may be mesas epitaxially grown on the surface or regions diffused or ion-implanted in the surface, are positioned so that radiation (20) absorbed between them generates photocarriers which are able to diffuse and/or drift to the zones. Also described is an array of transducers in which the photovoltages developed across a plurality of pairs of zones are added in series.

Abstract: Discrete InP-InGaAsP mesa double heterostructure lasers have been fabricated by a batch process in which the laser mirrors are formed by chemically etching the wafer from the top surface down into the substrate. A feature of the process is that the metal contact on the top surface is recessed within the periphery of an overlying mask, and the etching time is controlled so that the contact is not undercut by the sidewalls of the mesa. Another feature is the use of a self-limiting etchant which etches the mirrors smoothly and at a faster rate than the sidewalls. Preferably, the mirrors etch isotropically and the sidewalls etch preferentially along crystallographic planes. Also described is subsequent batch processing (e.g., forming mirror coatings) and on-wafer testing of the etched-mirror lasers.

Abstract: A current-switched gate is described which comprises two Josephson tunnel junctions and a small resistor in a triangular loop. Directly combined bias and control currents flow through one junction in the zero-voltage state, causing the switching. The second junction and the resistor provide isolation between input and output after switching. Switching speeds of a few tens of picoseconds and the microwatt power dissipation are attained. Latching as well as nonlatching schemes and memory circuits are described.

Abstract: A double heterostructure laser having a pair of opposite-conductivity-type, wide bandgap cladding layers separated by a narrower bandgap active region is characterized in that the active region includes a low-loss waveguide layer and contiguous therewith a narrower bandgap active layer in the form of a narrow strip which extends along the longitudinal (resonator) axis of the laser. Suitable lateral current confinement means, such as reversed biased p-n junctions, are provided to constrain pumping current to flow in a narrow channel through the active layer. Lasers of this type exhibit relatively high pulsed power outputs (e.g., 400 mW), linear L-I characteristics, stable fundamental transverse mode and single longitudinal mode oscillation. In another embodiment the surfaces of the waveguide layer adjacent the active layer are provided with distributed feedback gratings.

Abstract: A semiconductor barrier Josephson junction device (10) comprises a semiconductor body (12) having a pair of parallel noncoplanar major surfaces (14, 16) which are joined along parallel edges (18, 20) by an oblique surface (22) which forms an acute angle with the major surfaces. Superconductive electrodes (24, 26) on the major surfaces extend near to the parallel edges and thereby define the tunneling barrier as the semiconductor region which extends along the oblique surface. Also described is an array of such junctions connected in series.

Abstract: Suitably modified molecular beam epitaxy (MBF) techniques are used to synthesize single crystal, periodic monolayer superlattices of semiconductor alloys on single crystal substrates maintained below a critical growth temperature. Described is the fabrication of periodic structures of (GaAs).sub.n (AlAs).sub.m, where m and n are the number of contiguous monolayers of GaAs and AlAs, respectively, in each period of the structure. As many as 10,000 monolayers were grown in a single structure. Also described is the MBE growth of (Al.sub.x Ga.sub.1-x As).sub.n (Ge.sub.2).sub.m, quasi-superlattice and non-superlattice structures depending on the particular values of n, m and the growth temperature. Waveguides, heterostructure lasers and X-ray reflectors using some of the structures are also described.

Abstract: A lift-off mask for the patterned deposition of thin films comprises a three layer sandwich of photoresist-aluminum-photoresist on a substrate. Deposition occurs through an opening in the top photoresist layer and through larger size (i.e., undercut) openings in the aluminum and bottom photoresist layers. The top layer of photoresist remains on the mask during deposition and defines the pattern, the bottom photoresist is fully exposed and in the openings provides an undercut which prevents edge tearing during lift-off, and the aluminum layer (typically 50-200 Angstroms thick) protects the bottom layer of photoresist from dissolving during formation of the top photoresist layer. Also described is a technique in which the edges of thin films are tapered by depositing them from a direction oblique to the substrate surface and by rotating the substrate during deposition. These techniques are specifically discussed in the context of fabricating Josephson junction devices.

Abstract: A process for hermetically sealing an optical fiber to a metal housing is described. An optical fiber 12 is threaded through a thick-walled metal tube 10 which has a bore 11 of slightly larger diameter than the fiber. The tube and fiber are inserted in a pneumatically operated collet and uniform radial pressure is applied to the tube to form a unitary hermetic assembly. Metal tube 10 is characterized in that it has or, prior to forming the assembly, is annealed to have a Rockwell hardness of less that 15 T 15. At this value the metal is soft and the pressure required to cause the metal to cold flow around the fiber is less than that required to break the fiber. The tube is then soldered or otherwise secured in a hole in the housing, thus completing the hermetic seal. Such a seal is useful in hermetic packaging of optical devices. It is advantageous over the prior art for its simplicity and inexpensiveness. The technique is suited to high yield mass production of reliable seals.

Abstract: A DC powered, self-resetting Josephson junction logic circuit relying on relaxation oscillations is described. A pair of Josephson junction gates are connected in series, a first shunt is connected in parallel with one of the gates, and a second shunt is connected in parallel with the series combination of gates. The resistance of the shunts and the DC bias current bias the gates so that they are capable of undergoing relaxation oscillations. The first shunt forms an output line whereas the second shunt forms a control loop. The bias current is applied to the gates so that, in the quiescent state, the gate in parallel with the second shunt is at V=O, and the other gate is undergoing relaxation oscillations. By controlling the state of the first gate with the current in the output loop of another identical circuit, the invert function is performed.

Abstract: A planar field effect transistor (FET) includes a plurality of spaced-apart, floating Schottky barrier, epitaxial metal gate electrodes which are embedded within a semiconductor body. A drain electrode and a gate control electrode are formed on one major surface of the body whereas a source electrode, typically grounded, is formed on an opposite major surface of the body. The FET channel extends vertically between the source and drain, and current flow therein is controlled by application of suitable gate voltage. Two modes of operation are possible: (1) the depletion regions of the control gates and the floating gates pinch off the channel so that with zero control gate voltage no current flows from source to drain; then, forward biasing the control gate opens the channel; and (2) the depletion regions of the control gates and the floating gates do not pinch off the channel, but reverse biasing the control gate produces pinch off.

Abstract: An oblique shadow deposition technique for altering the profile of grating relief patterns on surfaces is described. In one aspect the technique essentially represents a method whereby a series of grating masks may be superimposed in precise registration with each other. By appropriate choice of deposition angle, deep grooves may be generated from shallow profiles, rounded or sinusoidal profiles may be transformed to structures with planar vertical walls, and symmetric profiles may be made asymmetric.

Abstract: The effusion cell for molecular beam epitaxy apparatus consists of a pyrolytic BN cylindrical crucible surrounded by a heating coil. The position of the heating coil is maintained by a plurality of ceramic rods extending parallel to the cylinder axis with notches along their length for engaging the heating coil. The ceramic rods are secured by a retaining ring near the front of the crucible and an apertured disk near the back of the crucible. The entire assembly is surrounded by a foil heat shield.

Abstract: Electrolytic deposition of gold results in the formation of undesirable reducible gold III species in the electroplating bath which interfere with the current efficiency and make the prediction of gold thickness based on applied current impossible. Addition of a small quantity of hypophosphorous acid to the plating bath when the current efficiency has dropped below a certain minimum, chemically reduces accumulated gold III species and scavenges dissolved oxygen. Thus, the current efficiency is restored to about 100%. The hypophosphorous acid treatment is particularly advantageous in a phosphate buffered bath because no foreign ions are introduced into the solution.

Abstract: Parallel channels are separated by ridges formed in a semiconductor body in such a way that each channel is wider at its base than at its top. Molecular beam epitaxy is used to deposit semiconductor layers on the ridges and in the channels. Because each channel is narrower at its top than at its base, the configuration is essentially self-masking. That is, the layers in the channel are physically separate from those on the ridges, as would be metallic contacts deposited on the layers. This technique is employed in the fabrication of a plurality of self-aligned, stripe geometry, mesa double heterostructure junction lasers.

Abstract: A vertical field effect transistor (10) includes a relatively wide bandgap, lowly doped active layer (18) epitaxially grown on, and substantially lattice matched to, an underlying semiconductor body portion (13). A mesa (20) of lower bandgap material is epitaxially grown on and substantially lattice matched to the active layer. A source electrode (22) is formed on a bottom major surface (34) of the semiconductor body portion, a drain electrode (24) is formed on the top of the mesa, and a pair of gate electrode stripes (26) are formed on the active layer adjacent both sides of the mesa. When voltage (V.sub.G), negative with respect to the drain, is applied to the gate electrodes, the depletion regions (28) thereunder extend laterally in the active layer until they intersect, thereby pinching off the flow of current in the channel extending from the drain and source electrodes.

Abstract: Surface recombination current in GaAs devices is reduced by means of a semi-insulating, oxygen, iron or chromium doped monocrystalline layer of AlGaAs grown by MBE. The AlGaAs layer is grown on a GaAs body and is then masked. Diffusion of suitable impurities through a window in the mask converts the exposed portions of the AlGaAs layer to low resistivity and modifies the conductivity of the underlying zone of the GaAs body. The peripheral portions of the AlGaAs layer, however, remain semi-insulating and are effective to reduce the surface recombination velocity - diffusion length product by more than an order of magnitude.