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Molybdenum Trioxide (MoO3) films are grown on Si(100) substrates by reactive RF magnetron sputtering in plasma containing a mixture of Argon and Oxygen, using a pure Molybdenum target. In this paper, we report the deposition of (MoO3) films on Si(100) substrates under varying gas flow (O2 + Ar gas) (20 sccm to 30 sccm with the duration of deposition~ 1hr) by RF reactive magnetron sputtering at room temperature. To get crystalline MoO3 films annealing in O2 environment at 500 °C for 4 h is done. Phase formation and orientation of the film is characterized by Glancing incidence X-ray diffraction (GIXRD). The identification of the orthorhombic MoO3 phase is investigated by XRD and Raman spectroscopy. Raman lines at 819 cm-1 and 995 cm-1 are due to the (A1g, B1g) symmetric stretching (Mo-O–Mo) bond and asymmetric stretching band (Mo=O) respectively. Surface morphology and cross-sectional image of the deposited thin films were investigated by FE-SEM image. UV-Visible reflectance and cross-sectional FE-SEM image confirm the thickness of the MoO3 films with oxygen-rich and oxygen deficient phase formation occur. Reverse leakage current density of 20 sccm 1hr sample is low (1×10-6 mA/cm2) as compared to 30 sccm 1hr sample (1×10-3 mA/cm2). The higher leakage is due to crack formation during the ex-situ annealing of MoO3 films. This MoO3 films can be used in Gas sensing and switching devices.

This paper discussed about the morphological and electrical properties of c-axis oriented aluminium nitride (AlN) thin films grown on Si (100) and Si (110) substrates by direct current (DC) reactive sputtering technique. Both the films showed intense (002) peak with the texture coefficient (γ) of 3.1 and 2.8 corresponding to Si (100) and (110) substrates. The AlN/Si (110) have grain sizes (20–30 nm) compared to the relatively denser grains (30–40 nm) of the film on Si (100) substrate. Both the films exhibited slanted columnar structures with slanting angle of 15° (Si (100) substrate) and 20° (Si (110) substrate). The dielectric constant values of the films at low frequency are found to be 7.4 and 8.8 corresponding to the Si (100) and Si (110) substrates respectively. The variation in dielectric constant values over the low frequency regime seems to be due to the presence of trapped charges present in the AlN layer and AlN‑silicon interface (interface trap density~1012 cm-2 eV−1). The flat band voltages are found to be 0.85 V and − 0.35 V corresponding to the Si (100) and (110) substrates respectively. The AlN/Si (100) film showed poor leakage current density ~ 10−4 A/cm−2 as compared to AlN/Si (110) (~ 10−5 A/cm−2). The AlN films exhibited dielectric breakdown field of 4.4 MV/cm and 6.6 MV/cm corresponding to the Si (100) and Si (110) substrates respectively.

In this paper, we simulated the DC IV characteristics using Two Dimensional Analytical model. This model has included piezo-electric-effect, virtual gate formation between gate and drain and its effect on the 2-DEG conduction current. The proposed model shows excellent agreement with the ATLAS simulated data.

This paper presents the structural, optical, and electrical characteristics of AlN thin films on Si (111) substrate grown by DC magnetron sputtering technique for MEMS applications. The grown AlN thin films (thickness: 680, 900, and 1200 nm) exhibited polycrystalline wurtzite structure with preferred orientations along directions. The mean grain size of the films varies from ~ (15–40 nm) of AlN layers. As the thickness increases, the FTIR E1 (TO) peak broadening of the films varies from 165 cm−1, 151 cm−1, and 128 cm−1, respectively. The electrical characterization of AlN/Si (111) is studied by fabricating the Metal-Insulator-Semiconductor (MIS) structure. The static dielectric constant of the AlN films varies from 6.80 to 5.94 as the films' thickness increases. The variation in dielectric constant values are due to the existence of interface trapped charges (interface trap density of states ~1010 - 1011 cm−2 eV−1) present in the AlN-silicon interface. The presented article corroborates the structural, morphological, optical, and electrical characteristics of AlN films on Si (111) with varying thickness comprehensively for piezoelectric MEMS applications.

This paper reports the study of surface-related mechanisms to explain the high reverse leakage current observed in the in-house fabricated Si3N4 passivated AlGaN/GaN High Electron Mobility Transistors. We propose that the Si3N4/AlGaN interface in the un-gated regions provides an additional leakage path between the gate and source/drain and may constitute a large component of reverse current. This surface related leakage component of current exhibits both temperature and electric field dependence and its Arrhenius behavior has been experimentally verified using Conductance Deep Level Transient Spectroscopy and temperature dependent reverse leakage current measurements. A thin interfacial amorphous semiconductor layer formed due to inter diffusion at Si3N4/AlGaN interface has been presumed as the source for this surface related leakage. We, therefore, conclude that optimum Si3N4 deposition conditions and careful surface preparation prior to passivation can limit the extent of surface leakage and can thus vastly improve the device performance. (C) 2016 Elsevier B.V. All rights reserved.

Ion implantation of the amphoteric dopant Si compared to the natural n-type dopant S in GaSb epitaxial films results in a higher dopant activation with better surface morphology and crystallinity. GaSb films were grown by molecular beam epitaxy (MBE) on semi-insulating GaAs (001) substrates. Ion implantation for both ions was carried out at an energy of 50 keV and a fluence of 1 × 1015 ions/cm2. Raman spectroscopy revealed a better crystallinity as well as a lower Sb out-diffusion for Si implantation as compared to S after annealing. Van der Pauw Hall measurements confirm the donor nature of the amphoteric dopant Si and with a dopant activation that is 3 times higher than the natural donor S. The electrical activation for both implants increases significantly after thermal annealing. Using temperature (20 K–300 K) vs conductivity measurement and displacement per atom (dpa) estimation, implantation-induced defect-related conduction mechanism is discussed. The results suggest the scope of Si as a viable n-type dopant in GaSb.

A two-dimensional analytical model involving a multi-phonon tunneling process at high static electric fields in AlGaN/GaN HEMTs to explain the drain current collapse has been attempted. This model successfully explains the sudden recovery of drain current at a particular drain voltage for different applied gate voltages due to an exponential increase in emission rate from surface donors. This phenomenon leads to a rapid collapse of the virtual gate formed from the gate edge towards the drain, eventually causing a full recovery of the drain current to an uncollapsed condition. This paper also includes the effect of an increase in channel temperature by self-heating due to applied gate and drain voltages.

Experimental observations of simultaneous existence of fast and slow trap states in AlGaN/GaN HEMTs are presented here. The presence of traps with time constants (0.1 ms ∼ 0.1 s) and activation energies (0.3 eV∼0.54 eV) was detected from transconductance dispersion and admittance curves. These fast traps may assist the high gate leakage currents in AlGaN/GaN HEMTs. The slower traps having the time constants of more than 0.1 s, along with faster traps, may be responsible for hysteresis in the observed output I-V characteristics.

Admittance spectroscopy of pristine AlGaN/GaN metal-semiconductor interface reveals the distributed trap activation energy in the order of 0.24 eV by mercury probe capacitance-voltage (C-V) measurements. The trap densities of states (D it ) of these traps were extracted in the range of ∼1.9×1012 eV−1cm−2 with the reverse bias voltage ranging from −5 Volts to 0 Volt. A very good fitting of admittance spectra (G/ω) was obtained by using the time constants of these traps. The dispersion in the capacitance was corrected to obtain an accurate depth profile of the hetero-structures.

The experimentally observed inverse temperature dependence of the reverse gate leakage current in AlGaN/GaN HEMT is explained using a virtual gate trap-assisted tunneling model. The virtual gate is formed due to the capture of electrons by surface states in the vicinity of actual gate. The increase and decrease in the length of the virtual gate with temperature due to trap kinetics are used to explain this unusual effect. The simulation results have been validated experimentally.