A INTRODUCTION

A reliable set of structural data is essential for many investigations of both epilayers and bulk material. Even the structural assessment and analysis of SiGe epilayers which are presently of enormous interest for novel and high performance device applications requires the knowledge of sufficiently precise material data. In this Datareview we review some crystallographic data such as crystal structure and lattice parameters and the phase diagram of silicon germanium alloys.

B CRYSTAL STRUCTURE

Silicon and germanium, which both crystallize in the diamond lattice, are completely miscible forming Si _1-xGe _x solid solutions with x ranging from 0 to 1. The space lattice of diamond consists of two face-centred-cubic (fcc) lattices which are displaced a quarter of the space diagonal. A perspective drawing of the unit cell is depicted in FIGURE 1. The space group of the diamond structure is -Fd3m. The cubic unit cell contains eight atoms that occupy the following positions:

Figure 1: Diamond crystal structure. Each atom is tetrahedrally bonded to four nearest-neighbours as displayed by the rods.

The fractions denote the height above the base in units of the cube edge. In this structure each atom is bonded to four nearest-neighbours with a distance of arranged at the corners of a...