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Title: Specific features of molecules' pyrolysis on the epitaxial surface in the case of growth of the Si{sub 1-x}Ge{sub x} layers from hydrides in vacuum

Abstract

Specific features of molecules' pyrolysis in the case of growth of Si{sub 1-x}Ge{sub x} films from hydrides in vacuum are considered in the context of kinetic approximation on the basis of a growth experiment. The type of solution characteristic of the kinetic problem was studied in relation to the values of the system's parameters for a scheme of decomposition of monohydrides of Si and Ge with a dominant role of SiH{sub 2} and GeH{sub 2} radicals in the pyrolysis process. It is shown for the first time that, in the system under consideration, there can exist at least two types of solutions that differ radically from each other in the rate of incorporations of atoms into the growing layer and in the degree of filling of the surface states with products of molecules' pyrolysis. The type of solution characteristic of the actual experiment is determined from the condition for the segregation-related accumulation of Ge atoms at the growth surface of the Si{sub 1-x}Ge{sub x} film. Numerical analysis performed in relation to the growth temperature made it possible to estimate the rate of the monohydrides' decomposition and the values of the factor of incorporation of Si and Ge adatoms into themore » crystal. The estimate of the characteristic decomposition time for monosilane yields the value of 3-4 s at the growth temperatures of 450-700 deg. C; for monogermane, this value is about 2 s.« less

Authors:
;  [1]
  1. Russian Academy of Sciences, Institute for the Physics of Microstructures (Russian Federation)
Publication Date:
OSTI Identifier:
21088459
Resource Type:
Journal Article
Resource Relation:
Journal Name: Semiconductors; Journal Volume: 41; Journal Issue: 1; Other Information: DOI: 10.1134/S1063782607010137; Copyright (c) 2007 Nauka/Interperiodica; Article Copyright (c) 2007 Pleiades Publishing, Ltd; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; CRYSTALS; EPITAXY; FILMS; GERMANIUM ALLOYS; GERMANIUM HYDRIDES; HYDRIDES; LAYERS; NUMERICAL ANALYSIS; PYROLYSIS; SILICON ALLOYS; SILICON COMPOUNDS; SURFACES

Citation Formats

Orlov, L. K., E-mail: orlov@ipm.sci-nnov.ru, and Ivin, S. V. Specific features of molecules' pyrolysis on the epitaxial surface in the case of growth of the Si{sub 1-x}Ge{sub x} layers from hydrides in vacuum. United States: N. p., 2007. Web. doi:10.1134/S1063782607010137.
Orlov, L. K., E-mail: orlov@ipm.sci-nnov.ru, & Ivin, S. V. Specific features of molecules' pyrolysis on the epitaxial surface in the case of growth of the Si{sub 1-x}Ge{sub x} layers from hydrides in vacuum. United States. doi:10.1134/S1063782607010137.
Orlov, L. K., E-mail: orlov@ipm.sci-nnov.ru, and Ivin, S. V. Mon . "Specific features of molecules' pyrolysis on the epitaxial surface in the case of growth of the Si{sub 1-x}Ge{sub x} layers from hydrides in vacuum". United States. doi:10.1134/S1063782607010137.
@article{osti_21088459,
title = {Specific features of molecules' pyrolysis on the epitaxial surface in the case of growth of the Si{sub 1-x}Ge{sub x} layers from hydrides in vacuum},
author = {Orlov, L. K., E-mail: orlov@ipm.sci-nnov.ru and Ivin, S. V.},
abstractNote = {Specific features of molecules' pyrolysis in the case of growth of Si{sub 1-x}Ge{sub x} films from hydrides in vacuum are considered in the context of kinetic approximation on the basis of a growth experiment. The type of solution characteristic of the kinetic problem was studied in relation to the values of the system's parameters for a scheme of decomposition of monohydrides of Si and Ge with a dominant role of SiH{sub 2} and GeH{sub 2} radicals in the pyrolysis process. It is shown for the first time that, in the system under consideration, there can exist at least two types of solutions that differ radically from each other in the rate of incorporations of atoms into the growing layer and in the degree of filling of the surface states with products of molecules' pyrolysis. The type of solution characteristic of the actual experiment is determined from the condition for the segregation-related accumulation of Ge atoms at the growth surface of the Si{sub 1-x}Ge{sub x} film. Numerical analysis performed in relation to the growth temperature made it possible to estimate the rate of the monohydrides' decomposition and the values of the factor of incorporation of Si and Ge adatoms into the crystal. The estimate of the characteristic decomposition time for monosilane yields the value of 3-4 s at the growth temperatures of 450-700 deg. C; for monogermane, this value is about 2 s.},
doi = {10.1134/S1063782607010137},
journal = {Semiconductors},
number = 1,
volume = 41,
place = {United States},
year = {Mon Jan 15 00:00:00 EST 2007},
month = {Mon Jan 15 00:00:00 EST 2007}
}
  • The epitaxial growth of Si and Si{sub 1-x}Ge{sub x} alloys from molecular beams of gaseous Si (Si{sub 2}H{sub 6}) and Ge (GeH{sub 4}) hydrides on Si(001) substrates (Si gas-source molecular-beam epitaxy) has been studied using reflection high-energy electron diffraction (RHEED). Diffraction patterns reveal that Ge deposited on Si results in a Stranski-Krastanow growth mode with a change in surface reconstruction prior to the onset of three-dimensional growth. RHEED intensity oscillations measured during Si{sub 1-x}Ge{sub x} alloy growth indicate that below 600 {degrees}C, the addition of GeH{sub 4} flux to the substrate results in an enhanced growth rate (GR), but abovemore » 600 {degrees}C this phenomenon is not observed and the GR remains proportional to the Si{sub 2}H{sub 6} flux. Further, a temperature and flux dependent change in the growth rate, {Delta}Gr, is observed at the Si/Si{sub 1-x}Ge{sub x} interface. At low temperatures (<580 {degrees}C), the growth of several monolayers precedes the establishment of a constant alloy GR, indicative of a graded Ge composition in the interface region. This phenomenon is discussed in terms of the temperatures dependent reaction kinetics in this system during growth between 520-640 {degrees}C. 27 refs., 5 figs.« less
  • Epitaxial Si{sub 1{minus}{ital x}}Ge{sub {ital x}}(001) alloy films, with 0.15{le}{ital x}{le}0.30, were grown on Si(001) at temperatures {ital T}{sub {ital s}} ranging from 300 to 550{degree}C using hyperthermal Si (average energy {l_angle}{ital E}{sub Si}{r_angle}{approx_equal}18 eV) and Ge ({l_angle}{ital E}{sub Ge}{r_angle}{approx_equal}15 eV) beams. The deposition rate was 0.1 nms{sup {minus}1} and film thicknesses ranged from 30 nm to 0.8 {mu}m. The energetic Si and Ge beams are generated by bombarding Si and Ge targets with 1 keV Kr{sup +} ions from double-grid, multiaperture, broad ion-beam sources in a system geometry established based upon TRIM simulations of energy-dependent angular distributions of sputteredmore » and backscattered particles. A combination of high-resolution plan-view and cross-sectional transmission electron microscopy, high-resolution x-ray diffraction, Rutherford backscattering spectroscopy, channeling, and axial angular-yield profiles demonstrated that the films are of extremely high crystalline quality. Critical layer thicknesses {ital h}{sub {ital c}} for strain relaxation in these alloys were found to increase rapidly with decreasing growth temperature. For Si{sub 0.70}Ge{sub 0.30}, {ital h}{sub {ital c}} ranged from 35 nm at {ital T}{sub {ital s}}=550{degree}C to 650 nm at 350{degree}C compared to an equilibrium value of {approx_equal}8 nm. At even lower growth temperatures, {ital h}{sub {ital c}} becomes larger than critical epitaxial layer thicknesses, {approx_gt}1 {mu}m at 300{degree}C. In addition, atomic force microscopy studies showed that strain-induced roughening, which occurs at elevated growth temperatures, is strongly suppressed at {ital T}{sub {ital s}} between 300 and 400{degree}C with no indication of kinetic roughening. {copyright} {ital 1996 American Institute of Physics.}« less
  • B-doped Si{sub 1{minus}{ital x}}Ge{sub {ital x}} layers with Ge fractions, determined by Rutherford backscattering spectroscopy, ranging from 0 to 0.28 and B concentrations, from quantitative secondary-ion spectroscopy measurements, between 5{times}10{sup 16} and 4{times}10{sup 19} cm{sup {minus}3} were grown on Si(001) at temperatures {ital T}{sub {ital s}}=475{endash}575{degree}C by gas-source molecular beam epitaxy from Si{sub 2}H{sub 6}, Ge{sub 2}H{sub 6}, and B{sub 2}H{sub 6}. Film thicknesses ranged from 200 nm for alloys with {ital x}=0.28 to 800 nm with {ital x}=0.05 to 1.4 {mu}m for Si. Structural analyses by high-resolution x-ray diffraction and reciprocal lattice mapping combined with transmission electron microscopy showedmore » that all films were fully strained, with measured relaxations of only {approx_equal}4{times}10{sup {minus}5}, and exhibited no evidence of dislocations or other extended defects. The hole conductivity mobility {mu}{sub {ital c},{ital h}} in these layers increased continuously with increasing Ge concentrations, whereas the Hall mobility decreased yielding a Hall scattering factor that ranged from 0.75 for Si to 0.26 for Si{sub 0.72}Ge{sub 0.28} but was not strongly affected by B concentration. {mu}{sub {ital c},{ital h}}, with {ital C}{sub B}=2{times}10{sup 18} cm{sup {minus}3}, varied from 110 cm{sup 2}V{sup {minus}1}s{sup {minus}1} for Si{sub 0.95}Ge{sub 0.05} to 158 cm{sup 2}V{sup {minus}1}s{sup {minus}1} for Si{sub 0.72}Ge{sub 0.28}, compared to 86 cm{sup 2}V{sup {minus}1}s{sup {minus}1} for Si, in good agreement with Boltzmann transport model calculations accounting for changes in the valence-band structure due to the effects of both alloying and biaxial in-plane compressional strain. {copyright} {ital 1996 American Institute of Physics.}« less
  • The conditions of the epitaxial growth of high-quality relaxed Si{sub 1–x}Ge{sub x} layers by the combined method of the sublimation molecular-beam epitaxy and vapor-phase decomposition of monogermane on a hot wire are considered. The combined growth procedure proposed provides a means for growing Si{sub 1–x}Ge{sub x} layers with a thickness of up to 2 µm and larger. At reduced growth temperatures (T{sub S} = 325–350°C), the procedure allows the growth of Si{sub 1–x}Ge{sub x} layers with a small surface roughness (rms ≈ 2 nm) and a low density of threading dislocations. The photoluminescence intensity of Si{sub 1–x}Ge{sub x}:Er layers ismore » significantly (more than five times) higher than the photoluminescence intensity of layers produced under standard growth conditions (T{sub S} ≈ 500°C) and possess an external quantum efficiency estimated at a level of ~0.4%.« 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