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The current voltage characteristics and the low-frequency noise in high voltage 4H-SiC junction barrier Schottky diodes irradiated with high energy (15MeV) protons were studied at different temperatures and irradiation doses Φ from 3 x 1012 cm-2 to 1 x 1014 cm-2. Irradiation led to the increase of the base resistance and the appearance of slow relaxation processes at small, V ≤ 0.2 V, and at rather high, V ≥ 2 V, forward voltages. The characteristic times of these relaxation processes ranged from ~1 µs to 10³s. The exponential part of the current-voltage characteristic was only weakly affected by irradiation. The temperature dependence of the base resistance changed expo-nentially with temperature with activation energy Ea ~ 0.6 eV, indicating that the Z1/2 level plays a dominant role in this process. The temperature increase also led to the increase of the ideality factor from 1.05 at 25 °C to 1.1 at 172 °C. At elevated temperatures and high forward voltages V > 2-4 V, the current voltage characteristics tend to be super-linear. It is concluded that at high voltages, the space charge limited current of majority carriers (electrons) and hole injection from the p-n regions play an important role in the formation of the current voltage characteristic. The frequency dependences of noise spectral density S of proton irradiated Schottky diodes have the unusual form of S ~ 1/f05. [ABSTRACT FROM AUTHOR]

We report on the effect of forward current stress on the low frequency noise in the 4H–SiC rectifier p+-n diodes rated at 20 and 10 kV. The 4H–SiC diodes with 20 kV blocking voltage were the most sensitive to the forward current stress. Even the stress by the current density j=13 A/cm2 for 30 min led to a noticeable increase in the forward voltage drop and changes in the noise spectra. The stress decreased the level of the 1/f noise but led to the appearance of the burst noise. Stress at higher current densities (50 A/cm2) led to the disappearance of the burst noise and to a further increase in the forward voltage drop. Diodes with 10 kV blocking capability were more resistant to the forward current stress. However, they also demonstrated a decrease in the 1/f noise as a result of the 60 min stress at j=100 A/cm2. [ABSTRACT FROM AUTHOR]

The low frequency noise was studied in 4H-SiC metal oxide semiconductor field effect transistors (MOSFETs) in the frequency range from 1 Hz to 100 kHz. 1/f (flicker) noise dominated in output noise over the entire frequency range and for a wide range of drain and gate biases. The dependence of the relative spectral noise density, SI/Id2, on the drain current, Id (at constant drain voltage, Vd), was qualitatively different from typical dependences for n-channel Si MOSFETs. In Si MOSFETs, in strong inversion, SI/Id2 usually decreases as ∼1/Id2 and tends to saturate in the subthreshold region, whereas in SiC MOSFETs under study, SI/Id2∝Id-0.5 for the currents varying from the deep subthreshold regime to the strong inversion. [Similar dependences were often observed in amorphous and polycrystalline thin film transistors (TFTs).] The effective field effect mobility of 3–7 cm2/V s extracted from the measured I-V characteristics is almost as low as that in amorphous Si TFTs. This result might be explained by a high density of localized states near the conduction band in the thin ion implanted silicon carbide layer. The energy dependence of trap density responsible for the noise was extracted for the states located close to the bottom of conduction band. [ABSTRACT FROM AUTHOR]

Fast and ultrafast switch-on processes in p-n diodes at very high current densities j and very short current rise time τ0 have been investigated analytically. It is demonstrated that even at relatively modest values of the rate of current density rise dj/dt, the switch-on transient fundamentally differs from that in the “classical” quasineutral mode. The switch-on processes occur in modes with broken neutrality. The base resistivity is modulated by fast hole and electron waves that propagate toward each other at the maximum possible (saturation) velocities. The conditions for the appearance of fast waves have been established. Analytical expressions for the initial stage of propagation of these waves have been derived. Adequate computer simulation confirms the analytical results. [ABSTRACT FROM AUTHOR]

Electron-hole scattering (EHS) affects the operation of all bipolar semiconductor devices at a high current density. From a physical point of view, EHS has always been considered an additional "frictional mechanism" for free carriers. Because any friction is a dissipative process, the main conclusion of numerous studies devoted to EHS is that the EHS increases the forward voltage drop across semiconductor devices. As a consequence, the inclusion of EHS inevitably raises the energy loss in bipolar devices. It is shown in this paper that EHS leads to a decrease in the forward voltage drop across bipolar devices in some important cases. This decrease may be substantial from a practical point of view. [ABSTRACT FROM AUTHOR]

The parameters of electron-hole scattering (EHS) in silicon carbide (SIC) are estimated by analyzing pulsed isothermal current-voltage characteristics of 6.0 kV 4H-SiC diodes over a wide range of current densities (10[sup 0] - 10[sup 4] A/cm²) and external temperatures (293-553 K). The efficiency of EHS in SiC is approximately two times higher than that in Si and 60 times higher than that in GaAs. The EHS makes a very essential contribution to voltage drop across SiC bipolar devices at high forward current densities. [ABSTRACT FROM AUTHOR]

Presents information on a study which fabricated inversion- and depletion-mode n-channel metal-oxide-semiconductor field-effect transistors (MOSFET) on Β-SiC thin films grown by chemical vapor deposition. Device fabrication processes; Inversion-mode MOSFET; Drain current-voltage characteristics of a depletion-mode n-channel MOSFET; Observation on transconductances for the depletion-mode devices.

The bulk low frequency noise has been investigated in the 4H silicon carbide polytype. In the temperature range of 300-550 K the noise spectral density S is proportional to ƒ[sup -1.5], where ƒ is the measurement frequency. A very low noise level has been observed for the bulk noise. At 300 K, the Hooge constant α is as small as (2-4) × 10[sup -6] at ƒ = 20 Hz and α ≤ 5 × 10[sup -7] at ƒ = 1300 Hz. At T ≥ 600 K, the generation-recombination noise of a local level makes the main contribution into the total low frequency noise. The electron capture cross section σ of this level depends very strongly on temperature. In the temperature range of 620-700 K, the temperature dependence of σ can be expressed as σ ∼ exp(-E[sub 1]/kT), with an activation energy E[sub 1] as high as 2.7 eV. [ABSTRACT FROM AUTHOR]

Focuses on a study which characterized the SiO[sub2]/SiC interface through the high-low capacitance-voltage and conductance-frequency techniques. Experimental details; Results and discussion; Summary.