S. Simeonov

CNx/Si thin heterostructures for miniaturized temperature sensors

CNx/Si thin heterostructures were synthesized on Si 〈111〉 substrates by XeCl* excimer laser (λ=308 nm, τFWHM≅30 ns) ablation of nuclear grade graphite targets in 5 Pa nitrogen at room temperature. We investigated the current–voltage and capacitance–voltage characteristics of heterostructures obtained at 77 and 300 K. We monitored their conductance and capacitance as a function of the bias voltage applied, in the 100 Hz–1 MHz frequency range. Our results revealed the formation of deep localized electron states both inside the thin CNx films and at the CNx/Si substrate interface. The investigations evidenced that conduction through the CNx/Si thin heterostructure is of trap-assisted tunneling type. The experimental studies show quite a large decrease in capacitance and increase in conductance with the increase of applied frequency. The capacitance of the CNx/Si thin heterostructures increases with a decrease of the temperature. All the results support the potential development of new types of high sensitivi...

Trap-assisted tunneling at temperatures near 77 K in laser annealed Si n+-p junctions

The I–V characteristics of the n+-p Si junction diodes prepared by laser annealing of a p-type Si substrate, covered by a Si–P thin film, were measured in the 77–294 K temperature range. The I–V characteristics of these diodes were found to be independent of temperature in the range 77–120 K. It was established by C–V measurements that the acceptor concentration in the p side of these diodes is in the 1014–1015 cm−3 range. A trap-assisted tunneling mechanism was used to explain the temperature-independent conductivity of these laser annealed n+-p Si junction diodes. This tunneling mechanism is based on the recombination of tunneling holes in the n-side bulk adjacent to the space charge layer in the n+-p junction.

Study of the charge transport mechanism in pulsed laser deposited AlN: Si films

AlN films doped with Si (AlN:Si) were synthesized on p-Si(100) substrates by pulsed laser deposition. Al-AlN:Si-Si metal-insulator-silicon (MIS) structures were formed and their current-voltage characteristics measured at 77 K and 290 K were analyzed. The results revealed that the charge transport is carried through the AlN:Si-Si MIS structures by the mechanism of trap space charge limited current.

Trap-assisted tunneling in MOS structures with ultrathin SiO/sub 2/

The conductivity in SiO/sub 2//p-Si structures with 13 nm thick SiO/sub 2/, layer, subjected to hydrogen plasma at 300/spl deg/C, was investigated. The I-V characteristics of these structures were measured in the accumulation regime under electric field in the range (2-7) /spl times/ 10/sup 6/ V/cm at temperatures ranging 78-300 K. The obtained results suggest that the current through the oxide is carried out by inter-trap tunneling.

Conduction via deep levels in hydrogen plasma treated Au-Si Schottky structures

The forward current-voltage and 1 MHz capacitance-voltage characteristics of Au-Si structures, formed on hydrogen plasma treated substrates are studied in the temperature range 123-300 K. The results show that the current is due to electron tunneling via deep levels generated in the Si near to metal-silicon interface by plasma exposure.

Trap space charge limited current in pulsed laser deposited AlN:Cr films

AlN films, doped with Cr, were deposited on p-Si substrates by pulsed laser deposition (PLD). Al-PLD AlN:Cr-Si MIS structures were formed and their current-voltage and 1 MHz admittance characteristics were measured. The analysis of the direct and alternating current conductance and capacitance dependences of these MIS structures on applied voltage revealed that the charge transport in these films is carried out by the mechanism of trap space charge limited current.

The influence of deep levels on the admittance of MIS structures with sol-gel TiO 2 insulator film

The admittance- voltage characteristics of MIS structures with TiO2(La) dielectric films, have been measured in the 100 Hz-100 kHz test voltage frequency range. It has been established that the dielectric constant of these dielectric films increases with the decrease of the test voltage frequency. The conductance of these MIS structures increases with the test voltage frequency in the same 100 Hz-100 kHz frequency range. These admittance measurements are used to estimate the density of deep levels, responsible for observed dependence of the dielectric constant on the test voltage frequency in investigated MIS structures.

Inter-trap tunneling in SiO/sub 2/ films of hydrogen implanted n-Si/SiO/sub 2/ structures

Capacitance-voltage measurements at 77 and 300 K have shown that implantation of hydrogen ions with energy of 11 keV into the n-Si/SiO/sub 2/ structure generates defects in the 120 nm thick SiO/sub 2/ layer and at the Si/SiO/sub 2/ interface. In the accumulation mode tunnelling type conduction through the oxide is observed. It is shown that inter-trap tunnelling is responsible for this current.

Study of the conductivity in MIS structures with sol-gel TiO/sub 2/ dielectric films

The conductivity in sol-gel TiO/sub 2/ films deposited on n-Si was characterized by current-voltage measurements in a wide temperature range of 88-291 K. The results suggest that the conduction mechanism is the transport of electrons from the residual donors through the conduction band of TiO/sub 2/.

Dielectric properties of sol-gel TiO2(La) films

High dielectric TiO2(La) films deposited on the silicon waves by the sol-gel technique have been characterized by Spectroscopic Ellipsometry, Fourier Transformed Infrared Spectroscopy. Rutherford Backscattering Spectroscopy and electrical measurements. The microstructural, optical and electrical properties exhibit a strong dependence on the introduced lanthanum quality. For La/Ti > 0.1 all film properties are abruptly changed closer to that of pure lanthanum oxide.