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Source/drain electrodes contact effect on the stability of bottom-contact pentacene field-effect transistors AIP Advances 2, 022113 (2012) All-metallic lateral spin valves using Co2Fe(Ge0.5Ga0.5) Heusler alloy with a large spin signal Appl. Phys. Lett. 100, 052405 (2012) Contact transport of focused ion beam-deposited Pt to Si nanowires: From measurement to understanding Appl. Phys. Lett. 100, 053503 (2012) Ab initio quantum transport simulation of silicide-silicon contacts J. Appl. Phys. 111, 014305 (2012) Impact of fluorine treatment on Fermi level depinning for metal/germanium Schottky junctions Appl. Phys. Lett. 99, 253504 (2011) Additional information on J. Appl. Phys. A new mechanism of contact resistance formation in ohmic contacts with high dislocation density is proposed. Its specific feature is the appearance of a characteristic region where the contact resistance increases with temperature. According to the mechanism revealed, the current flowing through the metal shunts associated with dislocations is determined by electron diffusion. It is shown that current flows through the semiconductor near-surface regions where electrons accumulate. A feature of the mechanism is the realization of ohmic contact irrespective of the relation between the contact and bulk resistances. The theory is proved for contacts formed to III-V semiconductor materials as well as silicon-based materials. A reasonable agreement between theory and experimental results is obtained.

PACS 73.40.Gk, 81.05.Ea, 81.15.Hi, 85.30.Mn GaN/AlGaN double barrier resonant tunnelling structures grown by molecular beam epitaxy on GaN templates have been studied. Peaks in the I(V) characteristics are observed, which are similar to resonant peaks seen in conventional III-V based devices. However, the behaviour of the peaks in I(V) depend upon the previous charge-state of the device produced by electrical bias. Current instabilities are also observed at low voltages. The possible origin of the peaks in the I(V) at room temperature and 4 K is discussed. . Doublebarrier RTDs are the basic benchmark for quantum tunnelling devices. They have been made in a variety of materials systems, including AlGaAs, Si/Ge, and InAs/GaSb. If RTDs could be produced in the group III-Nitrides, a number of novel possibilities exist for development and exploitation. Due to the large band offsets, it should be possible to observe quantum behaviour at much higher temperatures than in other III-Vs. However for group III-Nitride tunnel barrier devices, two problems remain: the structural quality of the heterojunctions and the scattering by impurities due to the high background doping level. Both can destroy the translational invariance that leads to the conservation of electron momentum necessary for successful operation of RTDs.Conventional III-V RTDs are grown mainly by molecular beam epitaxy (MBE). For the group III-Nitrides, because no bulk GaN substrates were available, all structures were initially grown by hetero-epitaxy on sapphire or SiC substrates. Now, due to the availability of GaN templates, grown by hydride vapour phase epitaxy (HVPE) or metal organic vapour phase epitaxy (MOVPE), the structural and optical properties of MBE grown GaN films have been dramatically improved.The effective mass for GaN is about three times larger than for GaAs, so the quantum wells (QWs) in RTDs need to be thinner than in the arsenides [6]. For the tunnel barriers, the transmission coefficient (T) is given by T ~ exp (-2kb), where k = [2m*(V -E)]

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PACS 72. 70.+m, 73.40.Kp, 73.50.Td γ-ray radiation effect has been studied on transport and noise properties of high electron mobility transistors (HEMTs) with gate lengths in the range from 350 to 150 nm at room temperature. Current-voltage (I -V) characteristics of the devices demonstrate higher radiation hardness to 60 Co γ-rays up to doses of 10 9 Rad at larger gate lengths. This confirms the very important role of surface passivation for channel transport of the HEMTs. The deviation of the I -V characteristics parameters saturated current, transconductance, channel conductance, and threshold voltage does not exceed 20% at highest radiation dose. The noise spectra of pre-irradiated devices and after γ-irradiation show different frequency dependences corresponding to different fluctuation processes in the HEMTs. The results are confirmed by dynamic current measurements of the channel conductivity.

Abstract. We studied the noise spectra of molecule-free and molecule-containing mechanically controllable break junctions. Both types of junctions revealed typical 1/ f noise characteristics at different distances between the contacts with square dependence of current noise power spectral Ca, 87.15.hj, 85.65.+h.

The temperature dependence of contact resistivity q c in lapped silicon specimens with donor concentrations of 5 Â 10 16 , 3 Â 10 17 , and 8 Â 10 17 cm À3 was studied experimentally. We found that, after decreasing part of the q c (T) curve in the low temperature range, an increasing part is registered with increasing temperature T. It is demonstrated that the formation of contact to a lapped Si wafer results in the generation of high dislocation density in the near-surface region of the semiconductor and also in ohmic contact behavior. In this case, current flows through the metal shunts associated with dislocations. The theory developed is in good agreement with experimental results. V C 2012 American Institute of Physics. [http://dx

We address experimental and theoretical study of a two-dimensional electron gas transport at low and moderate electric fields. The devices under study are group-III nitride-based ͑AlGaN/GaN͒ gateless heterostructures grown on sapphire. The transmission line model patterns of different channel lengths, L, and of the same channel width are used. A strong dependence of the device I-V characteristics on the channel length has been found. We have developed a simple theoretical model to adequately describe the observed peculiarities in the I-V characteristics measured in steady-state and pulsed (10 Ϫ6 s) regimes. The effect of the Joule heating of a heterostructure is clearly distinguished. The thermal impedance and the channel temperature rise caused by the Joule self-heating have been extracted for the devices of different L at different values of dissipated power. The current reduction due to both self-heating and hot-electron effects is determined quantitatively as a function of the electric field.