A measure of the electron mobility anisotropy in n-type 4H and 6H-SiC has been obtained using the Hall effect over the temperature range 80K<T<600K. Hall mobility and resistivity data are collected from appropriately oriented bar patterns fabricated into high quality epitaxial material grown on (1100) or (1120)surfaces having total impurity concentrations 1017-1018 cm-3. The observed mobility ratio for 4H is μ[1120]/[0001] and is independent of temperature. For 6H, the ratio μ[1100]/[0001] decreases from ∼6.2 at 80K to ∼5.0 at 150K and is essentially constant (∼4.8) above 200K. A donor level near 0.6 eV is occasionally observed in 4H which reduces the high temperature electron mobility and introduces an apparent temperature dependence to the mobility ratio if nonuniformly distributed.

The persistent observation of polarization aging during repeated room-temperature switching of metastable thin-film ferroelectric potassium nitrate capacitors has led to the conjecture that the observed polarization decay is a direct consequence of a concomitant phase III to phase II structural transformation. Appropriate large area thin-film devices have been fabricated to perform this x-ray diffraction study of the phase stability of ferroelectric KNO3 devices during in situ electrical switching. As the initial remanent polarization of 7.5 μC/cm2 decreases to &lt;0.4 μC/cm2 in &lt;2×106 polarization reversals, the volume fraction of III-KNO3 remains constant, and no reflections from II-KNO3 appear. After complete polarization loss, however, the initial d spacings measured for III-KNO3 have increased an average 0.4%. Examination of the line shapes during aging reveals that the observed shift is not a continuous transition, but a convolution of reflections centered at the initial and final d spacings. This characteristic modification to the original cell, here designated III′-KNO3, occurs throughout the switched volume. The simultaneous loss of polarization and appearance of the expanded unit cell suggest that III′-KNO3 either pins the polarization or is itself nonferroelectric.

Transport and strain relaxation in wurtzite InAs-GaAs core-shell heterowires Appl. Phys. Lett. 98, 152103 (2011); 10.1063/1.3579251Competition between strain-induced and temperature-controlled nucleation of InAs/GaAs quantum dots

We have measured the nonlinear conductivity, the thermopower, and the narrow-band noise in TaS3 as a function of elastic strain e along the chain axis. Both the thermopower and the chargedensity-wave (CDW) conductivity are dependent on the temperature and c. history of the sample. There are indications that the CDW becomes commensurate at @=0. 5%, where (at most temperatures) (1) there is a maximum in the threshold field for nonlinear conductivity, (2) there are anomalies in the thermopower and resistance, and (3) the narrow-band noise disappears.

Valence band discontinuities at the heterojunctions between CdTe, ZnTe, and HgTe in the (100) orientation: Xray photoelectron spectroscopy study J. Vac. Sci. Technol. B 6, 773 (1988); 10.1116/1.584371 Determination of the (100) InAs/GaSb heterojunction valenceband discontinuity by xray photoemission core level spectroscopy J. Appl. Phys. 61, 5337 (1987); 10.1063/1.338270 Measurement of ZnSe-GaAs(110) and ZnSe-Ge(110) heterojunction band discontinuities by xray photoelectron spectroscopy (XPS)