The present work describes the growth of the first thin {0. 1 -2 pm) epitaxial films of pure bismuth using molecular-beam-epitaxy techniques. These structures were grown at elevated temperatures on single-crystal barium fluoride substrates of (111) orientation. Electron-microscope observations show the films to be featureless and defect free on the scale of 0.1 pm. The films grow with their trigonal axis parallel to the (111)axis of the substrate, and Laue-backscattering pictures show they are epitaxial. Mobilities at room temperature are on the order of 2 m V ' s ', and increase to over 10 at 20 K and 100 at liquid-helium temperatures. These values are far superior to those of other bismuth films grown to date, and approach mobilities observed in single-crystal bismuth. Further evidence of their single-crystal nature is given by the temperature-dependent resistivity below 6K, which is more akin to that of a bulk single crystal, rather than polycrystal, bismuth, and by the thickness dependence of the film mobilities, which are limited by scattering on film boundaries. The carrier density, as deduced from Hall measurements, is in the range {4-8)X 10 m at room temperature and decreases as the temperature is lowered, becoming constant below about 50 K at approximately SX10 ' m '. We also observe Shubnikov-de Haas oscillations in the resistivity and Hall coefBcient at 4.2 and 0.4 K. The carrier density calculated from the period of these oscillations correlates well with that found from Hall measurements.

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N-type conductivity and properties of carbon-doped InN(0001) films grown by molecular beam epitaxy J. Appl. Phys. 113, 033501 (2013); 10.1063/1.4775736 Improved electron mobility in InSb epilayers and quantum wells on off-axis Ge (001) substrates J. Appl. Phys. 111, 073525 (2012); 10.1063/1.3702820 Effect of dislocations on electrical and electron transport properties of InN thin films. I. Strain relief and formation of a dislocation networkWe have investigated the evolution of structural and electronic properties of highly mismatched InSb films, with thicknesses ranging from 0.1 to 1.5 m. Atomic force microscopy, cross-sectional transmission electron microscopy, and high-resolution x-ray diffraction show that the 0.1 m films are nearly fully relaxed and consist of partially coalesced islands, which apparently contain threading dislocations at their boundaries. As the film thickness increases beyond 0.2 m, the island coalescence is complete and the residual strain is reduced. Although the epilayers have relaxed equally in the ͗110͘ in-plane directions, the epilayer rotation about an in-plane axis ͑epilayer tilt͒ is not equal in both ͗110͘ in-plane directions. Interestingly, the island-like surface features tend to be preferentially elongated along the axis of epilayer tilt. Furthermore, epilayer tilt which increases the substrate offcut ͑reverse tilt͒ is evident in the ͓110͔ direction. High-resolution transmission electron microscopy indicates that both pure-edge and 60°misfit dislocations contribute to the relaxation of strain. In addition, as the film thickness increases, the threading dislocation density decreases, while the corresponding room-temperature electron mobility increases. The other structural features, including the residual strain, and the surface and interface roughness, do not appear to impact the electron mobility in these InSb films. Together, these results suggest that free-carrier scattering from the threading dislocations is the primary room-temperature mobility-limiting mechanism in highly mismatched InSb films. Finally, we show quantitatively that free-carrier scattering from the lattice dilation associated with threading dislocations, rather than scattering from a depletion potential surrounding the dislocations, is the dominant factor limiting the electron mobility.

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. semi-insulating GaAs or InP substrates have resulted in the development of magnetoresistors with excellent sensitivity and operating temperatures up to 285%. 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 llCV compounds. 2DEG layers in InSb and lnAs would be ideally suited for these devices. The,accumulation layer at t h e surface of InAs has been used to make magnetoresistors. Hall sensors and magnetotransistors. n-type doped thin lnSb films are used to make magnetoresistors that outperform Si-based Hall sensors, even with integrated amplification. We 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. We compare the output of different magnetic field sensing technologies, such as Si and GaAs Hall sensors, and NiFe-based magnetoresistors, with lnSb magnetoresistors. Recent developments in the growth of thin epitaxial layers of InAs and inSb on

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