Abstract: The inventive methods of making a semiconductor device, e.g., a laser, comprise thermal (e.g., 3-5 .mu.m wavelength) imaging of a powered, partially completed device. The thermal image is obtained with apparatus that is capable of forming a substantially diffraction-limited image on a sensor array with an acquisition time of no more than 0.1 seconds, preferable no more than 0.01 seconds. In preferred embodiments, the image has temperature resolution of 0.01.degree. C. or better. Exemplary apparatus is disclosed. The inventive method facilitates, for instance, early identification of devices that are likely to fail lifetime requirements.

Abstract: We have found that etching of a body that comprises exposed Si as well as a Ti-comprising metal layer (e.g., a patterned Ti/Pt layer) in an amine-based anisotropic etchant for Si (e.g., 100.degree. C. EDP) frequently results in undesirable changes in the Ti-comprising metal layer. We have also found that the changes can be substantially reduced or eliminated by electrolytic means, namely, by making the metal layer the anode in an electrolytic cell that contains the etchant.

Abstract: A new class of high temperature superconductive oxides is disclosed. An exemplary member of the class has nominal composition Pb.sub.2 Sr.sub.2 Y.sub.0.5 Ca.sub.0.5 Cu.sub.3 O.sub.8 and has a transition temperature T.sub.c (onset) of about 79K.

Abstract: The output of vertical cavity surface emitting layers (VC-SELs) generally lacks polarization stability due to polarization mode degeneracity. I have discovered that in the usual (001) laser geometry polarization mode degeneracity can be removed if the active region of the laser is selected such that the active region lacks mirror symmetry with respect to any plane normal to the [001] crystal direction. Exemplarily, the active region comprises one or more asymmetrical quantum wells, e.g., quantum wells having a saw-tooth profile. The invention can also be embodied in edge emitting lasers, but embodiment in VC-SELs is preferred.

Abstract: The disclosed method of shaping a diamond body, typically a polycrystalline diamond (PCD) wafer or film, involves forming a, typically patterned, layer of an "etch-retarding" material on a surface of the diamond body, followed by etching with an appropriate etchant (e.g., molten Ce). Etch-retarding materials are selected from the materials that have low (typically less than 5%) mutual solubility with the etchant at the processing temperature, and that essentially do not form an intermetallic compound with the etchant at the processing temperature. Among etch-retarding materials are Ag, Ca, Mg, Cr, Mo, W, V, Nb, Ta, Ti, Zr, Hf, B, P, and alloys thereof, as well as ceramics such as oxides, nitrides, carbides and borides, e.g., WO.sub.2, TiO.sub.2, MoC, TiC, Fe.sub.4 N, ZrN, MoN, CeB.sub.6 and Mo.sub.2 B. The etch-retarding material typically will be of appropriately chosen, non-uniform thickness, with the thickness at a given point depending on the amount of diamond material that is to be removed at that point.

Abstract: Disclosed is an article that comprises a superconductor-insulator (s-i) layer structure. The superconductor material has nominal composition Ba.sub.1-x M.sub.x BiO.sub.3-y (M is K, Rb, or K and Rb, 0.35<x.ltorsim.0.5, 0<y.ltorsim.0.25). In some preferred embodiments the insulator is a Ba- and Bi containing oxide, exemplarily BaBi.sub.2 O.sub.4, Ba.sub.1-x M.sub.x BiO.sub.3 (0.ltoreq.x<0.35), or Ba.sub.1-x Bi.sub.1+x O.sub.3 (0.ltoreq.x.ltorsim.0.5). In other embodiments the insulator is an insulating oxide with the NaCl structure (e.g., Mg.sub.1-x Ca.sub.x O), an insulating perovskite (e.g., BaZrO.sub.3 ), an insulator with the K.sub.2 NiF.sub.4 structure (e.g., Ba.sub.2 PbO.sub.4), an insulating fluoride with the BaF.sub.2 structure (e.g., Ba.sub.1-x Sr.sub.x F.sub.2), or an insulating fluoride with the NaCl structure (e.g., LiF). Disclosed are also advantageous methods of making an article according to the invention.

Abstract: New solder compositions which can have improved mechanical properties are disclosed. In a preferred embodiment, the solder comprises a matrix material and magnetically dispersed particles. A desirable dispersion of the magnetic particles in the matrix material, is accomplished by applying a magnetic field to the molten matrix material containing magnetic particles and solidifying it in the presence of the magnetic field. The particle-dispersed microstructures improve the mechanical properties of the solder composition. The improved solder composition can be made into a powder to be used in solder paste, cream or reshaped while substantially retaining the improved mechanical properties.

Abstract: Disclosed is a method of making InP-based DFB lasers that can reliably mitigate or substantially prevent erosion of the grating during overgrowth. The method comprises contacting, prior to overgrowth, the grating with a sulfurcontaining aqueous medium, e.g., 80 parts by weight H.sub.2 O/20 parts by weight ammonium sulfide.

Abstract: In a preferred embodiment, the disclosed method of making a compound semiconductor (e.g., InP, GaAs) device comprises etching of a semiconductor body by exposure of the body to a chemical beam or beams that comprise an etching medium (e.g., PCl.sub.3, AsCl.sub.3) and a precursor chemical (e.g., trimethylindium, trimethylgallium), followed by chemical beam epitaxy (CBE) growth of semiconductor material on the etched surface without exposure of the semiconductor body to the ambient atmosphere. Presence of the precursor chemical in the etching beam can result in significantly improved surface morphology, with attendant high quality re-growth. Multiple etching/growth sequences are facilitated by the almost instantaneous (e.g., about 1s) switching between the etching and growth modes that is possible in a reactor according to the invention.

Abstract: Broadband in-line gratings in optical waveguides are disclosed. The gratings have a bandwidth of at least 2 nm (preferably at least 4 nm) and a peak reflectivity of at least 70% (preferably at least 90%). Exemplarily, such gratings can be formed in H.sub.2 -treated Si-based fibers that support a normalized index change of at least 10.sup.-3. Gratings according to the invention can be used, for instance, to form pump radiation reflectors in an optical fiber communication system with Er-doped fiber amplifiers, or to flatten the amplifier gain curve. The gratings can be of the blazed or non-blazed type.

Abstract: The disclosed novel heterojunction bipolar transistor, to be referred to as the enhanced diffusion transistor (EDT), comprises a base of composition selected such that the base bandgap narrows from emitter towards collector in substantially step-wise fashion, resulting in N (N.gtoreq.2) substantially flat levels in the base bandgap. The height .DELTA..sub.j of the steps in the bandgap is greater than kT (typically at least about 30 meV), and also greater than the threshold energy of an appropriate rapid inelastic minority carrier scattering mechanism (e.g., optical phonon scattering, plasmon scattering) in the base material. The presence of the "steps" in the base bandgap of the EDT can, in consequence of the resulting strongly accelerated diffusive minority carrier transport in the base, lead to, e.g., improved high frequency characteristics, as compared to otherwise identical prior art (N=1) transistors.

Abstract: Novel optical fiber devices (amplifiers and lasers) are disclosed. The devices comprise one or more optical "cavities", depending on the type of device. The cavities typically are formed by means of in-line refractive index gratings in a length of silica-based optical fiber. The gratings typically have peak reflectivity of at least 98%. Use of such cavities enables CW pumping of the devices, making the devices suitable for use in optical fiber communication systems. In an exemplary embodiment the device is a Raman amplifier for 1.3 .mu.m signal radiation, and in another exemplary embodiment the device is a Raman laser having an output suitable for pumping an Er-doped fiber amplifier. An exemplary pump radiation source is a laser diode-pumped CW Nd:YAG laser.

Abstract: 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.

Abstract: In some applications of distributed feedback (DFB) lasers, it is important that the coupling constant .kappa. be closely controlled. This is not easily achieved, frequently resulting in low yield of acceptable devices. I have discovered that variations in .kappa. can be reduced if the DFB laser is designed such that the thickness t.sub.s of a spacer layer (between the active layer and the Bragg grating) is within about .+-.10% of the value t.sub.o /(1-.alpha.), where t.sub.o is the modal decay length, and .alpha. is a parameter which characterizes the fractional variation of t.sub.o with fractional changes in layer thickness.

Abstract: We have discovered that coherent variation of at least two laser parameters can result in improved device performance, e.g., in pure amplitude or frequency modulation at frequencies substantially above 1 GHz, or in previously unattainable modulation frequencies. Among the relevant laser parameters are pumping rate, optical gain coefficient, photon lifetime, confinement factor, effective carrier temperature, output frequency and spontaneous emission factor. Exemplarily, the pumping rate and the optical gain are coherently varied such that the output radiation is free of chirp, or the output frequency and the effective carrier temperature are coherently varied such that the output radiation has constant amplitude.

Abstract: 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.

Abstract: Disclosed is a laser/fiber mount that can advantageously be used in laser transmitter packages for a variety of purposes, including pump laser packages for optically amplified optical fiber transmission systems and fiber-to-the-home systems. Both laser and fiber are attached to the same unitary body, preferably a Si body. An integral heater serves to melt a quantity of solder that serves to bond the fiber to the body after alignment of the fiber to the laser. A relatively thick dielectric layer underneath the heater provides a large thermal impedance, insuring that the temperature of the unitary body is at least 50.degree. C. (preferably 150.degree. C.) less than that of the solder.

Abstract: The disclosed heterojunction bipolar transistor, to be referred to as the "coherent" transistor (CT), is capable of providing gain above the conventionally defined cut-off frequencies f.sub.T and f.sub.max. Substantially, mono-energetic (average energy .DELTA.) carriers are injected in beam-like fashion into the base, with kT<.DELTA.<hv.sub.opt, where k, T and h have their conventional meaning, and v.sub.opt is the frequency of the lowest relevant optical phonon in the base of width W.sub.B. Exemplarily, W.sub.B is about 100 nm, .DELTA. is about 20 meV, the CT comprises Si.sub.1-x Ge.sub.x or III/V material, with the base being doped n-type. The CT utilizes substantially collisionless minority carrier transport through the base, and is designed such that, at an operating temperature which typically is .ltorsim.77K, the variance of the average base transit time (.DELTA..tau..sub.B) is much less than the base transit time .tau..sub.B, typically less than 0.5 .tau..sub.B, preferably about .tau..sub.

Abstract: The disclosed tunable (wavelength and/or focal length) laser typically is a surface emitting laser that comprises a multilayer structure that comprises the lower Bragg reflector and the active region. A layer of electro-optic material (typically liquid crystal material) is in contact with the top surface of the multilayer structure, and means are provided for applying a voltage across the layer of electro-optic material. In one exemplary embodiment, the layer is inside the laser cavity, making the laser wavelength tunable. In another exemplary embodiment the laser is a Z-laser that focuses the output radiation, with the multilayer structure comprising also the upper Bragg reflector. In this embodiment the layer of electro-optic material is outside the laser cavity, and the laser has tunable focal length. A still further embodiment is both wavelength- and focal length-tunable. Lasers according to the invention can be advantageously used in a variety of applications, e.g.

Abstract: 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.