Optical Transmission, Photoluminescence, and Raman Scattering of Porous SiC Prepared from p-Type 6H SiC

Abstract

The optical transmission, temperature-dependence of the photoluminescence (PL), and Raman scattering of porous SiC prepared from p-type 6H-SiC are compared with those from bulk p-type 6H-SiC. While the transmission spectrum of bulk SiC at room temperature reveals a relatively sharp edge corresponding to its band gap at 3.03 eV, the transmission edge of porous SiC (PSC) is too wide to determine its band gap. It is believed that this wide edge might be due to surface states in PSC. At room temperature, the PL from PSC is 20 times stronger than that from bulk SiC. The PL PSC spectrum is essentially independent of temperature. The relative intensities of the Raman scattering peaks from PSC are largely independent of the polarization configuration, in contrast to those from bulk SiC, which suggests that the local order is fairly random.

Fabrication and surface passivation of porous 6H-SiC by atomic layer deposited films

“…4(b), the transmittance of porous samples has been significantly decreased compared to the flat sample, especially for samples c and d. After anodic etching, the porous 6H-SiC layers are still crystalline and they should be transparent for the wavelength above bandgap. However, the observed low transmittance performance of porous 6H-SiC sample is attributable to the enormous surface states [4]. …”

“…Porous SiC is a potentially attractive material for light emitting diodes (LEDs), photodetectors, sensors and substrate for monocrystalline SiC epitaxy [1][2][3][4]. Among these applications, porous SiC has potential to realize fluorescent SiC based white LEDs [5][6][7].…”

“…Porous SiC was first fabricated by Shor et al [8] by using anodic etching method, which anodizing single crystal n-type 6H-SiC in hydrofluoric acid and under UV illumination. Since then, a lot of studies of porous SiC have been reported with specific changes in morphology, optical transmittance and photoluminescence (PL) properties after the formation of porous structures in both 6H and 4H n-type or p-type SiC wafers [4,5,[9][10][11][12][13][14][15].…”

“…To date, there are mainly two different interpretations: a) quantum confinement effect [5]; b) surface-state upon anodic etching [4,12,[16][17][18]. However, the large surface area also leads to an enhanced nonradiative recombination rate due to the surface damage caused by etching process [19].…”

Influence of Electrochemical Etching on Electroluminescence from n-Type 4H- and 6H-SiC

“…We describe characteristic luminescence from n-type SiC during porous etching in the dark under breakdown conditions. Matsumoto et al, 7 Petrovakoch et al, 8 and Kim et al 9 reported a strong enhancement of the roomtemperature photoluminescence from porous n-type 6H-SiC. Kim et al also noted an increase in emitted intensity for EL.…”