Papers by Author: Michel Mermoux

Abstract: Raman spectroscopy and photoemission microscopy were coupled as two complementary non-destructive optical techniques in order to study biased 4H-SiC pin diodes. These two characterization tools have been largely used for the study of semiconductors but the combination of these two techniques has hardly been reported so far. Some structural defects inducing the same electrical damage could be discriminated and identified. Temperature could be measured in operating devices and the influence of the diode operating mode on the Raman signal could be evidenced.

Abstract: A detailed investigation of the optical and electronic properties of the deep-level defect UD-4 is reported. This defect has recently been observed in 4H semi-insulating silicon carbide, but has hardly been studied yet. Both low temperature and temperature-dependent photoluminescence were collected from the defect. Zeeman spectroscopy measurements were performed as well as time-resolved photoluminescence.

Abstract: The transfer by wafer-bonding of single-crystalline SiC thin films to a polycrystalline SiC support to obtain a “quasi-wafer” is an attractive way for lowering the cost of silicon carbide wafers. Such a process needs high quality polycrystalline substrates, with controlled and high-level bulk properties (thermal conductivity, electrical resistivity) and with very low surface roughness and surface bowing. Currently, polycrystalline SiC wafers which are available are siliconized SiC or CVD processed SiC wafers. Siliconized ceramic wafers are very heterogeneous (mixture of 3C, 6H, 15R and silicon), while CVD ones are of better quality (homogeneous and textured 3C). However neither the siliconized SiC nor the CVD SiC can be CMP polished with low roughness over large dimension. In this paper, wafers with large and textured grains (> 1cm) are processed and characterized. The polishing of such structures is studied and optimized to obtain low surface roughness. To meet these requirements high temperature processes used for single crystal growth were selected. Structural investigations performed on the grown ingots showed an important influence of the used seed since no preferential crystallographic orientation was observed during the growth. The final polishing quality was of high level but step heights were observed between grains.

Abstract: Structural defects in SiC crystals were investigated and 4H-SiC pin devices were characterized by micro-Raman scattering and photoemission. With the experimental set-up presented, defects could be successfully detected in SiC crystals but stacking faults could not be detected with micro-Raman scattering, although they could be detected by photoemission. Residual stress could be evaluated in 4H-SiC devices, as well as the temperature increase associated with the devices powering. A good correlation was found between the characterization techniques used: micro-Raman scattering and photoemission.

Abstract: We have studied the application of optical techniques for the determination of the spatial distribution of electronic properties of highly aluminum doped p-type SiC wafers. Absorption and birefringence mapping are known to be sensitive characterization methods to determine the homogeneity of charge carrier concentration and defects in n-type SiC. In the case of highly p-type doped SiC these methods fail due to the opaque character of the material. In this paper we show that Raman spectroscopy which is a reflective method can be used in order to address the same materials properties like absorption and birefringence. The study was performed using medium doped p-type SiC:Al where optical transmission and reflection methods can be applied simultaneously.