Search

Heavily Al-doped 4H-SiC structures have been prepared by vapor phase epitaxy. Subsequent anneals have been carried out in an Ar atmosphere in a rf-heated furnace between 1500 degreesC and 2000 degreesC for 0.5 to 3 h. Secondary ion mass spectrometry has been utilized to obtain Al concentration versus depth as well as lateral distributions (ion images). Transmission electron microscopy (TEM) has been employed to study the crystallinity and determine phase composition after heat treatment. A solubility limit of similar to 2x10(20) Al/cm(3) (1900 degreesC) is extracted. Three-dimensional ion images show that the Al distribution does not remain homogeneous in layers heat treated at 1700 degreesC or above when the Al concentration exceeds 2x10(20) cm(-3). Al-containing precipitates are identified by energy-filtered TEM., QC 20100525

An optical emission microscopy technique with spatial and spectral resolution capabilities is applied for stability studies of 4H-SiC material properties. From the example of a 4H-SiC p(+)/n(-)/n(+) diode imaged at different stages of electrical overstress the mechanism of degrading performance is directly unveiled. We correlate this phenomenon with irreversible structural changes within the active region created by a nonuniform heating related stress. The stress-generated features are interpreted as multiple stacking faults spreading throughout the whole base region and nucleated in the vicinity of built-in defects and process-induced structural deficiencies., QC 20100525

Epitaxially grown 4H-SiC structures with several heavily Al doped layers were used. The samples were annealed in Ar atmosphere in a RF-heated furnace between 1500 and 2900 degreesC for 0.5 to 3h. Secondary ion mass spectrometry (SIMS) was used to measure the aluminum concentration versus;depth as well as the lateral distribution (ion images). Transmission electron microscopy (TEM) was employed to study the crystallinity and determine phase composition after heat treatment. A solubility limit of 2x10(20) Al/cm(3) at 2000 degreesC is extracted. Ion images of the lateral Al distribution reveal a pronounced dependence on the Al content. Precipitate formation occurs after heat treatment at 1700 - 2000 degreesC when the Al concentration exceeds 2x10(20) cm(-3) and energy-filtered TEM (EFTEM) shows that the precipitates contain Al., 3rd European Conference on Silicon Carbide and Related Materials, KLOSTER BANZ, GERMANY, SEP, 2000 NR 20140805

Heavily Al-doped 4H–SiC structures have been prepared by vapor phase epitaxy. Subsequent anneals have been carried out in an Ar atmosphere in a rf-heated furnace between 1500 °C and 2000 °C for 0.5 to 3 h. Secondary ion mass spectrometry has been utilized to obtain Al concentration versus depth as well as lateral distributions (ion images). Transmission electron microscopy(TEM) has been employed to study the crystallinity and determine phase composition after heat treatment. A solubility limit of ∼2×10²⁰ Al/cm³ (1900 °C) is extracted. Three-dimensional ion images show that the Al distribution does not remain homogeneous in layers heat treated at 1700 °C or above when the Al concentration exceeds 2×10²⁰ cm⁻³. Al-containing precipitates are identified by energy-filtered TEM.

Epitaxially grown 4H-SiC structures with several heavily Al doped layers were used. The samples were annealed in Ar atmosphere in a RF-heated furnace between 1500 and 2900 degreesC for 0.5 to 3h. Secondary ion mass spectrometry (SIMS) was used to measure the aluminum concentration versus,depth as well as the lateral distribution (ion images). Transmission electron microscopy (TEM) was employed to study the crystallinity and determine phase composition after heat treatment. A solubility limit of 2x10(20) Al/cm(3) at 2000 degreesC is extracted. Ion images of the lateral Al distribution reveal a pronounced dependence on the Al content. Precipitate formation occurs after heat treatment at 1700 - 2000 degreesC when the Al concentration exceeds 2x10(20) cm(-3) and energy-filtered TEM (EFTEM) shows that the precipitates contain Al.

Experimental evidence is given for transient enhanced diffusion of boron (B) in ion-implanted silicon carbide (SiC). The implanted B is diffusing several mu m into the samples when annealed at 1600 and 1700 degrees C for 10 min, but the in-diffused tails remain unaffected when the annealing times are increased to 30 min at the same temperatures. A lower limit of the effective B diffusivity at 1600 degrees C is determined to 7x10(-12) cm(2)/s, which is 160 times larger than the equilibrium B diffusivity given in the literature., QC 20150626

In n-type 6H-SiC epitaxial layers grown by vapor phase epitaxy, we find that in contrast to the majority of the epitaxial layer, where electrically active defects are observed with a concentration less than 1 X 10(-13) cm(-3), a region near the front surface contains defects with concentrations approaching 10(14) cm(-3). A relationship between the near-surface defects and metallic impurities is suggested by a Ti concentration of 1 X 10(16) cm(-3) in this region. The high concentration of near surface defects is found to significantly reduce the carrier lifetime. (C) 1998 American Institute of Physics. [S0021-8979(98)03007-2]., NR 20140805

Anode-shorted GTO thyristor samples were investigated by means of the free-carrier absorption (FCA) technique. Both the turn-on and turn-off processes were investigated as regards the two-dimensional carrier distribution for different stages of the transient cycles. The results are presented as carrier-map sequences, i.e., 3-D pictures of measured 2-D carrier distributions. Samples were formed as unit segments cut out from large-area devices, and associated with different degree of anode shorting, silicon thickness, and lifetime treatment. During investigation, the samples were inductively anode loaded, and as regards the turnoff process they were operated near the safe-operation limit. The measurements clearly illustrate the way carriers are transported in the sample when firing the device, and the turn-on process is visualized in steps by means of carrier-map sequences. These measurements are supported by computer simulations. The turn-off process is also visualized in carrier-map sequences measured from two perpendicular directions, and the maps show the critical electric-field expansion which always precedes a turnoff failure due to dynamic breakdown mechanisms. Further on, the effect of design-parameter variations, e.g., anode shorting pattern and carrier lifetime reductions, on destructive GTO turnoff phenomena are discussed.