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To obtain reduced specific contact resistivity, iodine donors and silver acceptors were ion-implanted into n-type and p-type (Bi,Sb)2(Se,Te)3 materials, respectively, to achieve >10 times higher doping at the surface. Implantation into n-type materials caused the specific contact resistivity to decrease from 1.7 × 10−6 Ω cm2 to 4.5 × 10−7 Ω cm2. Implantation into p-type materials caused specific contact resistivity to decrease from 7.7 × 10−7 Ω cm2 to 2.7 × 10−7 Ω cm2. For implanted thin-film superlattices, the non-implanted values of 1.4 × 10−7 Ω cm2 and 5.3 × 10−8 Ω cm2 precipitously dropped below the detection limit after implantation, ≤10−8 Ω cm2. These reductions in specific contact resistivity are consistent with an increase in tunneling across the contact.

The anisotropy ratios (parallel to the c axis versus perpendicular to the c axis) for the electrical resistivity, Seebeck coefficient, and thermal conductivity of horizontal Bridgman-grown n-type (Bi2Te3)90 (Sb2Te3)5 (Sb2Se3)5 and p-type (Sb2Te3)72 (Bi2Te3)25 (Sb2Se3)3 were measured at 300 K. The orientation having the largest thermoelectric figure of merit was perpendicular to the zone axis of the c planes (along the natural growth direction). For the n-type alloy, the maximum thermoelectric figure of merit was determined to be 3.2×10−3/K. For the p-type alloy, the maximum thermoelectric figure of merit was determined to be 3.6×10−3/K when compensated with tellurium only, and 3.8×10−3/K when compensated with both tellurium and iodine. These values represent a significant increase over previously reported p-type thermoelectric figure of merit values. Hall coefficient data coupled with Seebeck coefficient measurements suggest a difference in carrier transport phenomena caused by an increased compensation of holes in the p-type alloy without the deleterious precipitation of the tellurium-rich second phase.

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It has been observed that the low-level, pre-tunneling currents through thin gate oxides increased after the oxides had been stressed at high voltages. The number of traps inside of the oxide generated by the stress has been shown to increase as the 1/3 power of the fluence that had passed through the oxide during the stress. The increases in the low-level, pre-tunneling currents have been shown to be proportional to the number of stress generated traps in the oxide and not to the fluence during the stress. The voltage dependences of the excess low-level leakage currents were stress and measurement polarity dependent. Attempts have been made to fit the voltage dependences of the excess low-level currents to Fowler-Nordheim tunneling, Frenkel-Poole conduction or Schottky barrier lowering. The increase in the portion of the low-level, pre-tunneling current that was not dependent on stress/measurement polarity sequence was best fit using Schottky emission currents. The model that has been developed to describe the increases in the low-level currents has centered on trap-assisted currents through the oxides.

A new technique for measuring thermal conductivity with significantly improved accuracy is presented. By using the Peltier effect to counterbalance an imposed temperature difference, a completely isothermal, steady-state condition can be obtained across a sample. In this condition, extraneous parasitic heat flows that would otherwise cause error can be eliminated entirely. The technique is used to determine the thermal conductivity of p-type and n-type samples of (Bi,Sb) 2 (Te,Se) 3 materials, and thermal conductivity values of 1.47 W/m K and 1.48 W/m K are obtained respectively. To validate this technique, those samples were assembled into a Peltier cooling device. The agreement between the Seebeck coefficient measured individually and from the assembled device were within 0.5%, and the corresponding thermal conductivity was consistent with the individual measurements with less than 2% error.

The low-level leakage currents in thin silicon oxide films were measured before and after the oxides had been stressed at high voltages. Four components of current were identified. These components were the tunneling current, the capacitive current associated with the measurement sweep rate, a negative differential current associated with the voltage sweep through the changing oxide C-V characteristic, and an excess current that occurred after the high-voltage stress. The excess current was due to the charging and discharging of traps generated inside of the oxide by the high-voltage stress. The excess current was proportional to the number of traps generated in the oxide. The magnitude of the excess current could be changed by changes in the measurement procedures due to the charging and discharging of traps. A major portion of the stress-generated excess low-level leakage current may not be a current that flowed through the oxide, but may be a trap charging/discharging current. This paper will concentrate on describing the low-level pretunneling leakage currents and the measurement techniques needed to determine the properties of the excess leakage currents associated with the traps generated inside of the oxide.