Spatially Resolved Photoluminescence and Thermally Stimulated Luminescence in Semi-Insulating SiC Wafers
- PDF / 173,469 Bytes
- 6 Pages / 612 x 792 pts (letter) Page_size
- 51 Downloads / 154 Views
K2.9.1
Spatially Resolved Photoluminescence and Thermally Stimulated Luminescence in SemiInsulating SiC Wafers Yu. M. Suleimanov, S. Lulu, I. Tarasov, S. Ostapenko, S. E. Saddow, University of South Florida, Tampa, Florida, 33620, U.S.A. T. V. Torchinska, ISFM – National Polytechnic Institute, Mexico DF, Mexico V. D. Heydemann, M. D. Roth, O. Kordina, M. F. MacMillan, Sterling Semiconductor, Tampa, Florida 33619, U.S.A.
ABSTRACT We report on non-contact and non-destructive spatially resolved characterization of traps and luminescence centers in vanadium-free semi-insulating 6H-SiC. Two optical techniques were employed: photoluminescence (PL) mapping and thermally stimulated luminescence (TSL) imaging on SiC wafers. PL and TSL topography reveal inhomogeneity at the periphery regions of the wafers. Low-temperature PL spectra show broad bands with the maxima at 1.75eV and 1.2eV, including a sharp zero-phonon line at 1.344eV. The TSL glow curves at T>80K show different peaks in the visible and infrared bands. The luminescence spectrum of the 105K TSL peak replicates 1.75eV band, while the 120K peak corresponds to the 1.2eV band. Additionally, the high temperature TSL peak at 210K shows an excellent match with 1.344eV zero phonon line. The trap energies of different peaks are calculated. We discuss a model of complex defects composed of closely spaced electron (hole) trap and UD3 defect.
INTRODUCTION Semi-insulating SiC substrates are required for high-power and high-frequency applications. High resistivity wafers doped with vanadium, a deep compensating donor, have been commercially available for some time [1]. Alternatively, V-free SiC substrates with resistivity up to 1x109 Ω.cm at room temperature can be produced by incorporating deep defects of presumably intrinsic origin [2]. Industry requires fast non-destructive characterization methods to track the point and extended defects in full-size SiC wafers and epitaxial layers. In these regards, optical methods offer superior advantages. In this paper we report on SiC wafer diagnostics using two spatially resolved techniques. One is the traditional PL mapping when the excitation laser beam is sampling different regions of the wafer by scanning across the wafer’s surface. The second approach relies on the effect of thermally stimulated luminescence (TSL) and wafer snap-shot imaging. The TSL effect was previously applied to small SiC samples [3]. Recently, we demonstrated TSL diagnostics in fullsize p-type [4] and vanadium doped SiC wafers [5]. Strong spatial inhomogeneity of the traps and recombination centers was documented. In this paper, we report on PL/TSL spectroscopy of commercial grade vanadium-free semi-insulating 6H-SiC wafers and the correlation of the TSL imaging with PL mapping.
K2.9.2
EXPERIMENTAL Single-side polished semi-insulating SiC wafers (or there parts) of up to 50mm in diameter were explored. Wafer TSL images in the visible range were obtained using a digital camera utilizing a “snap-shot” technique. For detailed analysis, we measured TSL glow
Data Loading...
