A method of fabricating a semiconductor structure including the steps of providing a silicon substrate (10) having a surface (12), forming on the surface (12) of the silicon substrate (10), by atomic layer deposition (ALD), a seed layer (20;20') characterised by a silicate material and forming, by atomic layer deposition (ALD) one or more layers of a high dielectric constant oxide (40) on the seed layer (20;20').

Method for fabricating a semiconductor structure including a metal oxide interface with silicon

Discusses the properties of magnetic field sensors based on semiconductors such as Hall generators and magnetoresistors, and on magnetic metals, such as permalloy and the recently discovered 'giant magnetoresistance' metallic multilayers. Some emphasis is placed on the comparison between sensors made using these different technologies. Applications of magnetic field sensors in magnetic recording technology and in position sensing are discussed briefly. Typically a sensor has to detect the difference between a high and a low value of field, around an average, which is of the order of 10-3 T in recording applications, but can exceed 0.1 T in position sensors.

https://iopscience.iop.org/article/10.1088/0022-3727/26/8/001/pdf

Solid state magnetic field sensors and applications

We report the Au-assisted chemical beam epitaxy growth of defect-free zincblende InSb nanowires. The grown InSb segments are the upper sections of InAs/InSb heterostructures on InAs(111)B substrates. We show, through HRTEM analysis, that zincblende InSb can be grown without any crystal defects such as stacking faults or twinning planes. Strain-map analysis demonstrates that the InSb segment is nearly relaxed within a few nanometers from the interface. By post-growth studies we have found that the catalyst particle composition is AuIn2, and it can be varied to a AuIn alloy by cooling down the samples under TDMASb flux.

http://iopscience.iop.org/article/10.1088/0957-4484/20/50/505605/pdf

InAs/InSb nanowire heterostructures grown by chemical beam epitaxy.

This article comprehensively reviews the growth of III–V antimony-based semiconductor materials using metal-organic chemical vapor deposition (MOCVD). It does this by first discussing the general trends found for the growth of these materials. Next the specific growth techniques are discussed for each of the antimony-based systems including the binaries InSb, GaSb, and AlSb. The growth techniques used for many of the ternaries and quaternaries of these materials are also discussed. Following this a brief description of the use of dopants, novel organometallic sources and superlattices is presented. Next, the use of common characterization techniques is presented for different types of materials. A variety of the types of devices is then presented followed by a short summary and forecast of future directions that are currently being pursued in these materials.

The metal-organic chemical vapor deposition and properties of III–V antimony-based semiconductor materials

High quality epitaxial layers of compound semiconductor materials can be grown overlying large silicon wafers by first growing an accommodating buffer layer on a silicon wafer. The accommodating buffer layer is a layer of monocrystalline oxide spaced apart from the silicon wafer by an amorphous interface layer of silicon oxide. The amorphous interface layer dissipates strain and permits the growth of a high quality monocrystalline oxide accommodating buffer layer. The accommodating buffer layer is lattice matched to both the underlying silicon wafer and the overlying monocrystalline compound semiconductor layer. Any lattice mismatch between the accommodating buffer layer and the underlying silicon substrate is taken care of by the amorphous interface layer.

Semiconductor structure, semiconductor device, communicating device, integrated circuit, and process for fabricating the same

Narrow-gap semiconductors have been used for decades in the fabrication of magnetic field sensors, such as magnetoresistors and Hall sensors. Magnetic field sensors are, in turn, used in conjunction with permanent magnets to make contactless potentiometers and rotary encoders. This sensing technology offers the most reliable way to convert a mechanical movement into an electrical signal, and is widespread in automotive applications. Recent developments in the growth of thin epitaxial layers of InAs and InSb on semiinsulating GaAs or InP substrates have resulted in the development of magnetoresistors with excellent sensitivity and operating temperatures up to 285 degrees C. Magnetoresistors and Hall sensors require a very thin active semiconductor region, a high carrier density and a high room-temperature mobility. The best materials are narrow-gap III-V compounds. 2DEG layers in InSb and InAs would be ideally suited for these devices. The accumulation layer at the surface of InAs has been used to make magnetoresistors, Hall sensors and magnetotransistors. n-type doped thin InSb films are used to make magnetoresistors that outperform Si-based Hall sensors, even with integrated amplification. The authors describe device design criteria, materials requirements and a direct comparison of the three types of galvanomagnetic devices, magnetoresistors, Hall sensors and magnetotransistors, made from the same material. They compare the output of different magnetic field sensing technologies, such as Si and GaAs Hall sensors, and NiFe-based magnetoresistors, with InSb magnetoresistors.

http://iopscience.iop.org/article/10.1088/0268-1242/8/1S/093/pdf

Narrow-gap semiconductor magnetic-field sensors and applications

A magnetic field sensor apparatus that comprises an active layer of indium antimonide or indium arsenide supported on an elemental semiconductor substrate. Magnetoresistor sensors of indium antimonide and indium arsenide active layers on silicon and germanium substrate wafers are described. Means are described for providing reduced electric fields and parasitic conduction in the elemental semiconductor substrate. The means includes unique device geometries and buffer layers between the active layers and the substrate wafers.

Magnetic field sensor on elemental semiconductor substrate with electric field reduction means

For increased sensitivity, an improved position sensor includes a magnetic circuit in which the stationary portion includes a permanent magnet whose width is optimally 1.5 times the tooth pitch of the exciter portion of the sensor and the magnet face proximate the exciter includes a thin layer of ferromagnetic material over which is centered a narrow magnetic sensing element, such as a magnetoresistor. The sensing element has a width typically less than the tooth width. The sensing element includes a thin film of a monocrystalline semiconductive material, preferably having only a moderate bulk mobility and a larger band gap, such as indium arsenide. Current carriers flow along the length of the thin film in a surface accumulation layer, effective to provide a significant apparent increase in mobility and conductivity of said semiconductive material, and an actual increase in magnetic sensitivity and temperature insensitivity. The flux density is typically applied by appropriate magnet thickness or choice of magnet material without the need of a flux guide.

Position sensor including a thin film indium arsenide magnetoresistor on a permanent magnet

Thin films of InSb have been grown on insulating GaAs substrates using the metalorganic chemical vapor deposition technique with trimethyl indium and trimethyl antimony as reactants. We find that the mobilities obtained are usually low unless indium is predeposited onto the substrate. This indium predeposition technique greatly improves the yield of InSb films with mobilities of ~50000 crn2V−1S−1 at room temperature and a typical thickness of 2 microns. With this predeposition technique, the electron mobilities of these films become relatively independent of the vapor stroichiometry during growth and of the growth temperature. The electron mobilities are also very uniform across a wafer. These properties are obtained even when the film growth rate exceeds 2 μm/h.

Growth of high mobility InSb by metalorganic chemical vapor deposition

The growth and characterization of indium arsenide films grown on indium phosphide substrates by the metal organic chemical vapor deposition (MOCVD) process is reported. Either ethyl dimethyl indium or trimethyl indium were found to be suitable in combination with arsine as source compounds. The highest electron mobilities were observed in films nucleated at reduced growth temperature. Scanning electron microscopy studies show that film nucleation at low temperature prevents thermal etch pits from forming on the InP surface before growth proceeds at an elevated temperature. Electron mobilities as high as 21,000 cm2V−1 sec−1 at 300 K were thus obtained for a film only 3.4 μm thick. This mobility is significantly higher than was previously observed in InAs films grown by MOCVD. From the depth dependence of transport properties, we find that in our films electrons are accumulated near the air interface of the film, presumably by positive ions in the native oxide. The mobility is limited by electrons scattering predominantly from ionized impurities at low temperature and from lattice vibrations and dislocations at high temperature. However, scattering from dislocations is greatly reduced in the surface accumulation layer due to screening by a high density of electrons. These dislocations arise from lattice mismatch and interface disorder at the film-substrate interface, preventing these films from obtaining mobility values of bulk indium arsenide.

L. Green

Papers

Narrow-gap semiconductor magnetic-field sensors and applications

Magnetic field sensor on elemental semiconductor substrate with electric field reduction means

Position sensor including a thin film indium arsenide magnetoresistor on a permanent magnet

Growth of high mobility InSb by metalorganic chemical vapor deposition

Growth and characterization of indium arsenide thin films