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-x Ge 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 × 10 5 cm −2 , which is 4-10x lower than previously reported results.

Reduced pressure-chemical vapor deposition of intrinsic and doped Ge layers on Si(001) for microelectronics and optoelectronics purposes

“…It is, however, higher than what can be obtained when using a very thick (10 mm, typically) linearly or step graded SiGe buffer all the way from Si to pure Ge. Values of 2.1 Â 10 6 cm À2 [29] and very recently 1.5 Â 10 5 cm À2 [30] can indeed be found in the literature.…”

“…For such thick Ge layers, the surface presents a regular morphology which is some sort of convolution in-between mounds and a cross-hatch pattern, i.e. undulations along the /1 1 0S directions, as in SiGe virtual substrates [30,31]. The surface roughness is, however, rather low, especially when taking into account the very large lattice mismatch which has been accommodated (4.2% in-between Si and Ge).…”

High-temperature growth of very high germanium content SiGe virtual substrates

“…3), some severe quartz wall coating would occur for high Ge content virtual substrates grown in one step, altering the growth kinetics and inducing some significant particular contamination (flaking) [19]; (ii) it minimizes the strong surface roughening that occurs when ramping up the Ge concentration to high values [11,12,16]; (iii) it minimizes the threading dislocations bunching that results from rough surfaces and allows the threading arms of newly nucleated misfit dislocations to move, thereby minimizing the overall threading dislocation density [11].…”

“…Very high Ge content SiGe virtual substrates (50%p[Ge]p70%) can serve as templates for the growth of compressively strained Ge (c-Ge)/t-Si dual channels [6][7][8], with impressive hole mobility enhancements (up to 10) over bulk Si [9,10]. SiGe virtual substrates graded all the way up to pure Ge (with therefore low threading dislocations densities (TDDs) [11,12]) enable the monolithic integration of high-performance III-V optical devices (such as p + /n GaAs solar cells [13], AlGaInP resonant cavity light emitting diodes [14], etc.) on large area Si substrates etc.…”

Thin relaxed SiGe virtual substrates grown by low-energy plasma-enhanced chemical vapor deposition

“…LE-PECVD has been successfully used for conventional graded virtual substrates [21], at growth rates of up to 10 nm s À1 even at substrate temperatures lower than 500 1C, and for Ge concentrations up to 100% [22]. Some results indicating the promise of the new thin buffer design are published in Refs.…”