skip to main content
OSTI.GOV title logo U.S. Department of Energy
Office of Scientific and Technical Information

Title: Kinetic origin of island intermixing during the growth of Ge on Si(001)

Abstract

The effects of substrate temperature, growth rate, and postgrowth annealing on the composition of Ge islands grown on Si(001) were investigated with a combination of selective wet chemical etching and atomic force microscopy. A simple kinetic model comprising only surface diffusion processes can explain all the experimentally observed compositional profiles for pyramid and dome islands grown in the 560-620 deg. C range. From this model three-dimensional compositional maps were extracted. By performing annealing experiments a change in the composition of the domes was observed. This could be explained as the result of the islands' movement induced by alloying-driven energy minimization. Also in this case kinetically hindered bulk diffusion processes are not needed to explain the experimental observations.

Authors:
; ; ; ; ; ; ; ;  [1]
  1. Max-Planck-Institut fuer Festkoerperforschung, Heisenbergstrasse 1, D-70569 Stuttgart (Germany)
Publication Date:
OSTI Identifier:
20719830
Resource Type:
Journal Article
Resource Relation:
Journal Name: Physical Review. B, Condensed Matter and Materials Physics; Journal Volume: 72; Journal Issue: 19; Other Information: DOI: 10.1103/PhysRevB.72.195320; (c) 2005 The American Physical Society; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; ANNEALING; ATOMIC FORCE MICROSCOPY; CRYSTAL GROWTH; DIFFUSION; ETCHING; GERMANIUM; SEMICONDUCTOR MATERIALS; SILICON; SUBSTRATES; SURFACES

Citation Formats

Katsaros, G., Costantini, G., Stoffel, M., Esteban, R., Bittner, A.M., Rastelli, A., Denker, U., Schmidt, O.G., and Kern, K.. Kinetic origin of island intermixing during the growth of Ge on Si(001). United States: N. p., 2005. Web. doi:10.1103/PhysRevB.72.195320.
Katsaros, G., Costantini, G., Stoffel, M., Esteban, R., Bittner, A.M., Rastelli, A., Denker, U., Schmidt, O.G., & Kern, K.. Kinetic origin of island intermixing during the growth of Ge on Si(001). United States. doi:10.1103/PhysRevB.72.195320.
Katsaros, G., Costantini, G., Stoffel, M., Esteban, R., Bittner, A.M., Rastelli, A., Denker, U., Schmidt, O.G., and Kern, K.. Tue . "Kinetic origin of island intermixing during the growth of Ge on Si(001)". United States. doi:10.1103/PhysRevB.72.195320.
@article{osti_20719830,
title = {Kinetic origin of island intermixing during the growth of Ge on Si(001)},
author = {Katsaros, G. and Costantini, G. and Stoffel, M. and Esteban, R. and Bittner, A.M. and Rastelli, A. and Denker, U. and Schmidt, O.G. and Kern, K.},
abstractNote = {The effects of substrate temperature, growth rate, and postgrowth annealing on the composition of Ge islands grown on Si(001) were investigated with a combination of selective wet chemical etching and atomic force microscopy. A simple kinetic model comprising only surface diffusion processes can explain all the experimentally observed compositional profiles for pyramid and dome islands grown in the 560-620 deg. C range. From this model three-dimensional compositional maps were extracted. By performing annealing experiments a change in the composition of the domes was observed. This could be explained as the result of the islands' movement induced by alloying-driven energy minimization. Also in this case kinetically hindered bulk diffusion processes are not needed to explain the experimental observations.},
doi = {10.1103/PhysRevB.72.195320},
journal = {Physical Review. B, Condensed Matter and Materials Physics},
number = 19,
volume = 72,
place = {United States},
year = {Tue Nov 15 00:00:00 EST 2005},
month = {Tue Nov 15 00:00:00 EST 2005}
}
  • Thermally driven atomic transport in HfO{sub 2}/GeO{sub 2}/substrate structures on Ge(001) and Si(001) was investigated in N{sub 2} ambient as function of annealing temperature and time. As-deposited stacks showed no detectable intermixing and no instabilities were observed on Si. On Ge, loss of O and Ge was detected in all annealed samples, presumably due to evolution of GeO from the GeO{sub 2}/Ge interface. In addition, hafnium germanate is formed at 600 deg. C. Our data indicate that at 500 deg. C and above HfO{sub 2}/GeO{sub 2} stacks are stable only if isolated from the Ge substrate.
  • Surface morphological and compositional evolution during the initial stages of Si growth on Ge(001)2[times]1 by cyclic gas-source molecular beam epitaxy from Si[sub 2]H[sub 6] has been investigated using [ital in] [ital situ] reflection high-energy electron diffraction (RHEED), Auger electron spectroscopy, electron-energy-loss spectroscopy, and scanning tunneling microscopy, combined with post-deposition high-resolution cross-sectional transmission electron microscopy. The layers were deposited using repetitive cycles consisting of saturation Si[sub 2]H[sub 6] dosing at room temperature, followed by annealing for 1 min at 550 [degree]C. Film growth was observed to proceed via a mixed Stranski--Krastanov mode. Single-step-height two-dimensional growth was obtained for nominal Si depositionmore » thicknesses [ital t][sub Si] up to [congruent]1.5 monolayers (ML). However, the upper layer remained essentially pure Ge which segregated to the surface through site exchange with deposited Si as H was desorbed. At higher [ital t][sub Si], the Ge coverage decreased slowly, the surface roughened, and two-dimensional multilayer island growth was observed for [ital t][sub Si] up to [congruent]7.5 ML, where bulk reflections in RHEED patterns provided evidence for the evolution of three-dimensional island formula.« less
  • Si{sub 1{minus}x}Ge{sub x} layers with {ital x} ranging from 0 to 0.30 were grown on Si(001)2{times}1 substrates at temperatures ranging from 450 to 950thinsp{degree}C by gas-source molecular-beam epitaxy (GS-MBE) from Si{sub 2}H{sub 6} and Ge{sub 2}H{sub 6}. In the low-temperature surface-reaction-limited growth regime, the deposition rate R{sub SiGe} increases with increasing Ge concentration due to an enhancement in the hydrogen desorption rate resulting in a correspondingly higher steady-state dangling bond density. In the high-temperature impingement-flux-limited regime, where the steady-state hydrogen coverage approaches zero, R{sub SiGe} is controlled by the Si{sub 2}H{sub 6} and Ge{sub 2}H{sub 6} reactive sticking probabilities {italmore » S} which decrease with increasing Ge{sub 2}H{sub 6} flux but are not strongly temperature dependent. S{sub Si{sub 2}H{sub 6}} and S{sub Ge{sub 2}H{sub 6}} range from 0.036 and 0.28 on Si(001) to 0.012 and 0.094 during growth of Si{sub 0.82}Ge{sub 0.18} at T{sub s}=800thinsp{degree}C. In both growth regimes, large changes in R{sub SiGe} require only modest increases in incident Ge{sub 2}H{sub 6} to Si{sub 2}H{sub 6} flux ratios, J{sub Ge{sub 2}H{sub 6}}/J{sub Si{sub 2}H{sub 6}}, due to Ge segregation which is strongly coupled to the steady state hydrogen coverage. The Ge to Si ratio in as-deposited films increases linearly, while S{sub Ge{sub 2}H{sub 6}}/S{sub Si{sub 2}H{sub 6}} remains constant, with increasing J{sub Ge{sub 2}H{sub 6}}/J{sub Si{sub 2}H{sub 6}}. Hydrogen desorption and Ge segregation rates, together with Si{sub 2}H{sub 6} and Ge{sub 2}H{sub 6} reactive sticking probabilities, were quantitatively determined from D{sub 2} temperature-programmed desorption (TPD) measurements. The combined results from film growth kinetics and TPD studies, together with the assumption of linear superposition, were then used to develop a predictive model, with no fitting parameters, for R{sub SiGe}(T{sub s},J{sub Si{sub 2}H{sub 6}},J{sub Ge{sub 2}H{sub 6}}) during Si{sub 1{minus}x}Ge{sub x} GS-MBE. {copyright} {ital 1998 American Institute of Physics.}« less
  • The two-dimensional (2D) to three-dimensional (3D) morphological transition in strained Ge layers grown on Si(001) is investigated using scanning tunneling microscopy. The initial step takes place via the formation of 2D islands which evolve into small ({approx_equal}180 {angstrom}) 3D islands with a height to base diameter ratio of {approx_equal} 0.04, much smaller than the 0.1 aspect ratio of {l_brace}105{r_brace}-faceted pyramids which had previously been assumed to be the initial 3D islands. The ''prepyramid'' Ge islands have rounded bases with steps oriented along <110> and exist only over a narrow range of Ge coverages, 3.5--3.9monolayers.
  • Short-period (Si{sub m}/Ge{sub n}){sub N} superlattices (SSLs) are grown step by step on a Si(001) substrates by solid source molecular beam epitaxy. Using the step-graded SSLs as buffer layers, 2000 Aa uniform Si{sub 0.75}Ge{sub 0.25} alloy layers are grown on the same substrates. The growth temperature of the SSLs and uniform layers is 500{degree}C. In the SSLs layers, m and n are the number of monolayers of Si and Ge, respectively. N is the period of (Si{sub m}/Ge{sub n}) bilayers. The samples grown are characterized by x-ray diffraction, atomic force microscopy (AFM), and transmission electron microscopy (TEM) as a functionmore » of the step number of SSL layers. The SSLs show very smooth surfaces [the root-mean-square (rms) surface roughness is between 7 and 12 Aa]. A dramatic decrease in roughness is observed in the uniform Si{sub 0.75}Ge{sub 0.25} alloy layers, when even a one-step SSL is used as a buffer layer. A noticeable increase in rms roughness is seen in both SSL and alloy layers when the number of Ge monolayers is changed from one to two. AFM observation shows that the rms surface roughness behavior of the SSLs is reflected to their corresponding top alloy layers. The residual strains in alloy layers are considerably lower, with a maximum relaxation rate of about 80% for the sample with a seven-step SSL buffer. Cross-sectional TEM images show that strained SSL buffer layers effectively deflect threading dislocations in the substrate or confine the dislocations in the SSL buffer layers. {copyright} 2001 American Institute of Physics.« less