Structural characterization of thick, high-quality epitaxial Ge on Si substrates grown by low-energy plasma-enhanced chemical vapor deposition

Abstract

In this paper, we report on the growth of epitaxial Ge on a Si substrate by means of low-energy plasma-enhanced chemical vapor deposition (LEPECVD). A Si_1−xGe_x graded buffer layer is used between the silicon substrate and the epitaxial Ge layer to reduce the threading dislocation density resulting from the lattice mismatch between Si and Ge. An advantage of the LEPECVD technique is the high growth rate achievable (on the order of 40 Å/sec), allowing thick SiGe graded buffer layers to be grown faster than by other epitaxial techniques and thereby increasing throughput in order to make such structures more manufacturable. We have achieved relaxed Ge on a silicon substrate with a threading dislocation density of 1 × 10⁵ cm⁻², which is 4−10x lower than previously reported results.