Photoacoustic and transmission studies of SiC polytypes

Abstract

The optical bandgap energies (OBGE) of 3C, 15R, 6H and 4H-SiC have been investigate experimentally by transmission and photoacoustic spectroscopies. The measurements were performed on 470 mum thick wafers. The OBGE obtained from both spectroscopies for different polytypes show very good agreement. In order to have a better understanding of these materials calculations of eletronic band structure were performed by the full-potential linearized augmented plane wave (FPLAPW) method. For the OBGE the results are compared to the measurements agreeing closely over the energies of those polytypes

Cultured pearls and colour-changed cultured pearls: Raman spectra

“…A shift of the absorption edge from the violet range in 6H-SiC to the ultraviolet in 4H-SiC is consistent with literature data (Choyke and Patrick, 1961;de Oliveira et al, 1996). The spectra of the Russian sample 5 taken in different orientations are also consistent with reference data for nitrogendoped synthetic 4H-SiC (Biedermann, 1965;Lambrecht et al, 1998;Limpijumnong et al, 1999).…”

Spectroscopy studies of 4H-SiC

“…The physical properties of the large bandgap 4H-SiC make it a prominent material for high-power, high-temperature, and high-frequency devices. Devices like field effect transistors, bipolar storage capacitors, and ultraviolet detectors have been fabricated 1,2,3 .…”

“…In this work, we have investigated the optical properties of undoped and n-type 4H-SiC, both experimentally and theoretically. The transmission and photoacoustic spectroscopy techniques have been used for the measurement of the optical bandgap energy [3][4][5] . The total dielectric functions were determined by spectroscopic ellipsometry (SE), a powerful non-destructive technique for high accuracy measurements [5][6][7] .…”