Atsuko Uemoto

Characterization of the free‐carrier concentrations in doped β‐SiC crystals by Raman scattering

LO phonon‐overdamped plasmon coupled modes in n‐type epitaxial films of β‐SiC have been measured in the carrier concentration range from 6.9×1016 to 2×1018 cm−3. The carrier concentrations and damping constants are determined by line‐shape fitting of the coupled modes and compared with the values derived from Hall measurements. The concentrations obtained from the two methods agree fairly well. The Faust–Henry coefficient determined from the fitting is 0.35. The line‐shape analysis of the coupled mode has shown that the dominant scattering mechanisms in β‐SiC are deformation‐potential and electro‐optic mechanisms.

Temperature dependence of electrical properties of non‐doped and nitrogen‐doped beta‐SiC single crystals grown by chemical vapor deposition

Electrical properties of non‐doped and nitrogen‐doped n‐type β‐SiC films grown on Si substrates have been investigated at 70–1000 K. Those of non‐doped films remarkably depend on the Si/C ratio of the source gases. The highest mobilities of non‐doped films are 510 and 1330 cm2 V−1 s−1 at 296 and 71 K, respectively. The carrier concentrations are as low as 6×1016 cm−3 even at 1000 K. Ionization energies of 34 –37 meV for nitrogen donors and 19–25 meV for unknown donors of non‐doped films are obtained. Mobilities of both non‐doped and nitrogen‐doped films are dominated by lattice scattering at high temperatures and by impurity scattering at low temperatures. Nitrogen donors strongly affect the impurity scattering.

3C-SiC p-n junction diodes

3C‐SiC p‐n junction diodes are prepared on Si substrates by chemical vapor deposition growth with appropriate impurity doping, and their current‐voltage (I‐V) and capacitance‐voltage (C‐V) characteristics are studied. I‐V curves show good rectifying characteristics with a value of 3.3 for the ideal factor n and a reverse leakage current less than 10 μA at −5 V. The junction area is approximately 0.8 mm2. The built‐in voltage is around 1.4 V by C‐V measurements.

Inclined epitaxy of (411) beta silicon carbide on (511) silicon by chemical vapor deposition

Epitaxial growth of β‐SiC on Si(511) substrates has been carried out. Single‐crystalline β‐SiC films without warpage and cracking are grown by chemical vapor deposition. The epitaxial orientation of the film is determined using x‐ray precession camera. The orientation is inclined as SiC(411)//Si(511) coincident with the [011] axis, which should be compared with the parallel epitaxial growth on Si(100) or Si(111).

High-Temperature Characteristics of CVD-Grown β-SiC p-n Junction Diodes

g-SiC p-n junction diodes with a mesa structure are fabricated. using chemicalvapor d,eposition on Si substrates with an impurity doping d.uring the growth. Curuentvoltage and capacitance-voltage characteristics of the d-iod.es are measured. at high temperatures up to 500 oC. No significant d.egradation of the characteristics during iho hioln-tcmnar.ature operation occurs even at 500 oC. But the reetification becomes v rrv rrr6rr poor at high temperatures, with an increase in reverse leakage current and. an d.ecrease in built-in potential.