Materials Science Forum Vols. 679-680

Abstract: An isochronal annealing in the 100-1200 oC temperature range was carried out on 116 and 400 keV electron irradiated Al-doped 6H-SiC epitaxial layers. Electrical characterization of the epilayers, performed by Fourier-Transform Deep Level Transient Spectroscopy, revealed the presence of six levels in the band gap, in the 0.1-1.6 eV energy range. Their nature is discussed in the light of previous experimental and theoretical works found in the literature.

Abstract: Fe-implanted n-/p-type 4H-SiC samples were investigated by deep level transient spectroscopy (DLTS). In order to be able to separate Fe-related defect centers from defects caused by implantation damage, a corresponding Ar-profile was implanted. No Fe-related defects were observed in n-type 4H-SiC, while two Fe-related centers could be identified in p-type 4H-SiC. The electrical behavior of these centers is donor-like.

Abstract: Large-scale and gap error free calculations of the electronic structure of vacancies in 4H-SiC have been carried out using a hybrid density functional (HSE06) and an accurate charge correction scheme. Based on the results the carbon vacancy is proposed to be responsible for the Z1/2 and EH6/7 DLTS centers.

Abstract: p-type 3C-SiC samples were implanted by iron (Fe) and investigated by means of deep level transient spectroscopy (DLTS). Corresponding argon (Ar) profiles with similar implantation damage were implanted in order to distinguish between iron-related defects and defects caused by implantation damage. Two donor-like iron-related centers were identified in p-type 3C-SiC.

Abstract: Synchrotron White Beam X-ray Topography studies are presented of dislocation behavior and interactions in a new generation of seventy-six millimeter diameter, 4H-SiC wafers grown using Physical Vapor Transport under specially designed low stress conditions. Such low stress growth conditions have enabled reductions of dislocation density by two or three orders of magnitude compared to the lowest previously reported levels [1]. In this paper, detailed topography analysis will be presented of the deflection of threading dislocations with Burgers vectors of c and c+a onto the basal plane leading to reductions of the density of such dislocations down to levels of ~187 cm-2. The deflection of the latter type of dislocations produces complex faulted defect configurations and models for their creation are presented and discussed.

Abstract: Defects in cubic silicon carbide (3C-SiC) epilayers, that were grown using different techniques and on different substrates, were studied in terms of electrical activity and device limiting implications. An electrical characterization by conductive atomic force microscopy (C-AFM) showed that stacking faults (SFs) are normally the predominant type of defects that are electrically active at the semiconductor surface and, therefore, the most important defects that can affect the contact properties on these epilayers. It is also shown that an ultraviolet (UV) irradiation process can be used to suppress detrimental leakage currents passing through SFs that are carbon terminated at the semiconductor surface. Indeed, current-voltage characterization of Au/3C-SiC diodes showed a subsequent improvement of the Schottky behavior.

Abstract: The determination of dislocation density and in particular the dislocation distribution in SiC wafers is of particular interest for SiC crystal growth development and production. We present an image recognition tool allowing the wafer analysis with specific needs for SiC. In the first stage of expansion, micropipes are selected and counted from SiC wafers that have been etched by KOH.

Abstract: To quantitatively evaluate the efficacy of stacking fault (SF) reduction methods, Monte Carlo simulations are carried out to reveal the SF distribution on a 3C–SiC (001) surface. SF density decreases with increasing epitaxial layer thickness and reducing size of the substrates. Additionally, SF density depends on interactions between adjoining SFs: annihilation of counter SF-pairs or termination of orthogonal SF-pairs. However, the SF is not entirely eliminated when growth occurs on undulant-Si or switchback epitaxy due to “spontaneous SF collimation”. The simulation shows that effective SF reduction methods, those that enhance the SF termination or annihilation, can theoretically attain the SF density on 3C–SiC (001) below 100 cm-1.

Abstract: Selective etching on the surface of single-crystalline 4H-SiC was performed using ClF3 gas at 700 K and at atmospheric pressure in a cold wall reactor. The etch pits at the Si-face and C-face 4H-SiC surface may have relationship with the threading edge and screw dislocation.

Abstract: We have proposed a new wet etching recipe using molten KOH and Na2O2 as the etchant (“KN etching”) for dislocation revelation in highly doped n-type 4H-SiC (n+-4H-SiC). Threading screw dislocations (TSDs) and threading edge dislocations (TEDs) have been clearly revealed as hexagonal etch pits differing in pit sizes, and basal plane dislocations (BPDs) as seashell-shaped pits. This new etching recipe has provided a solution to the problem that conventional KOH etching is not effective for dislocation identification in 4H-SiC if the electron concentration is high (>mid-1018 cm-3). We have investigated the effect of SiC off-cut angle on KN etching and it has been shown that the “KN etching” is applicable for the n+-SiC substrate with off-angle from 0o to 8o.