Wafer-scale epitaxial germanium (100), (111), (110) films on silicon using liquid phase crystallization

Abstract

A wafer-scale method to obtain epitaxial germanium (Ge) on crystalline silicon (Si) using liquid-phase-crystallization (LPC) is presented. The technique provides a simple yet versatile method to grow epitaxial germanium on silicon with any crystallographic orientation: (100), (110) or (111). The process starts with amorphous Ge, which is melted and cooled in a controlled manner to form epitaxial germanium. LPC Ge films are continuous with an average grain-size of 2-5 μm. Rocking scan confirms that the LPC Ge is oriented with a threading dislocation density of ∼109 cm-2. The phi-scan confirms that LPC germanium is epitaxial with Ge (100), Ge (110) and Ge (111) showing four-fold, two-fold, and three-fold symmetry, respectively. The epitaxial quality of the Ge is influenced by the cleanliness of the Ge/Si interface; rate of cooling and ambient gas during LPC; and Ge layer thickness. Best films are obtained for 1 μm thick LPC Ge(100), cooled at ∼3-4 C/min in hydrogen ambient. Electron Hall mobility in these LPC Ge films is 736cm2/Vs, a high value that confirms the electronic quality of LPC Ge film.