R. Eckstein

SiC-bulk growth by physical-vapor transport and its global modelling

4H- and 6H-SiC bulk crystals have been prepared by physical vapor transport (PVT) both in resistively and inductively heated growth reactors. Epitaxial SiC layers were grown on the wafers by chemical vapor deposition. Structural and electrical material properties of the 1–1.4 inch boules and epitaxial layers were investigated by defect etching and optical microscopy, stress birefringence and Hall effect. Single crystalline material exhibits a low micropipe density MPD ≈ 70 cm−2 and stress level. Blocking characteristics of the epitaxial layers have been determined electrically revealing high breakdown fields of 1.8–1.9 MV/cm. Finally simulation results applying a process model of SiC PVT crystallization including heat and mass transfer and chemical reactions are presented.

Formation of micropipes in SiC under kinetic aspects

Abstract We measure the radii of micropipes at the {0001} surface of modified Lely grown 6H-SiC and the total step height of the accompanying growth spirals by using atomic force microscopy. The micropipes lie in the center of spirals; the total step height ranges between one and 19 unit-cells (1.5–28.5 nm). We fit Franks theory of hollow core dislocations as modified with regard to kinetic effects by Cabrera and Levine to these experimental results and obtain values for surface energy and supersaturation near the emergence point of the micropipe.

Micropipes and polytypism as a source of lateral inhomogeneities in SiC substrates

Abstract Structural and electrical inhomogeneities in SiC bulk crystals grown by the modified Lely sublimation method [1] in 〈0001〉 direction are investigated. Inclusions of different polytypes such as 15R in 6H material are observed on a macroscopic as well as a microscopic scale. Their size and number can be associated with the growth rate of the crystal. Beside the familiar micropipes, ‘nanopipes’ were observed by atomic force microscopy. Micropipes and nanopipes form centers of growth spirals related to the growth mechanism of the crystals under study. These micro- and nanopipes are a major source of structural and electrical inhomogeneities of SiC which are discussed in this paper.

The kinetic growth model applied to micropipes in 6H-SiC

Abstract In this study we investigated the as-grown [0001] Si surface of modified Lely-grown 6H-SiC using atomic force microscopy. We found micropipes that lie in the center of growth spirals whose radii ranged between 25 and 6000 nm. The screw component of the Burgers vector of the micropipe, which is synonymous with the total step height of the growth spiral, ranged from 1 to 25 unit-cells (1.5–37.5 nm). We fitted Franks theory of hollow core dislocations, as modified by Cabrera and Levine concerning kinetic effects, to these experimental results and obtained values for surface energy and supersaturation at the inner side of the micropipe.

Growth and Characterization of 2″ 6H-Silicon Carbide

For the growth of 2″ 6H-SiC a sublimation growth process was developed. By different means of characterization crystal quality was evaluated. Higher defect densities, mainly in the periphery of the crystals were found to be correlated to unfavourable process conditions. Improvement of thermal boundary conditions lead to a decreased defect density and better homogeneity over the wafer area.