Papers by Author: Aurelie Thuaire

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: 4H-SiC pin diodes were fabricated on epitaxial layers grown by Sandwich Sublimation Method (SSM). I-V and photoemission measurements were conducted on these devices. These measurements show hot spots responsible for a soft breakdown and evidence triangular shape defects previously observed in 4H-SiC pin diodes made on CVD epitaxial layers. These results agree with the morphology studies which indicate that the SSM-grown layers have a higher number of structural defects than their counterparts.

Abstract: The defects were investigated in p+nn+ 4H-SiC diodes by observing the forward-biasinduced light emission through the substrate. The spatial intensity distribution, the temporal evolution and the spectral content of the electroluminescence (EL) signal have been measured in order to detect, identify and understand the defect formation during forward-bias application. It was found that, exept from the dislocations inside the epilayers, mesa etching is a main cause for the formation of extended defects. To our knowledge, for the first time, reduction of mesa-etchinginduced defects is shown in this investigation.

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.