Optical control of growth of AlxGa1−xAs by organometallic molecular beam epitaxy

Abstract

Using spectroellipsometry, we obtain information on the near-surface composition x of epitaxial AlxGa1−xAs layers during crystal growth by organometallic molecular beam epitaxy and use this information to regulate the flow of triethylaluminum to the growth surface. The resulting closed-loop control system maintains the imaginary part of the dielectric response of thick AlxGa1−xAs films constant to an equivalent compositional precision better than ±0.001 over extended periods of time.

Real-time optical techniques and QMS to characterize growth in a modified commercial OMVPE reactor

“…This trajectory is essentially an exponential spiral that begins at the value of <ε> where growth begins and ends at the value of <ε> corresponding to that of bulk GaP when the GaP layer becomes optically thick. 12 It is clear that this does not provide a good representation of the data. The other extreme, the triangles, supposes that GaP growth originally begins as islands, which we model as a Bruggeman mix of 10% c-GaP and 90% voids.…”

“…In particular, real-time spectroscopic ellipsometry (SE) has been used to restrict the wide range of OMVPE operating parameters, thereby making it possible to achieve successful growth in a minimum number of runs. 3 SE is also the first and only technique to successfully demonstrate sampledriven closed-loop control of epilayer composition, 5,6,12 including graded compositions, 13 thickness, [14][15][16] growth rate, 17 and sample temperature. 14 Mass-sampling techniques, particularly quadrupole mass spectrometry (QMS), provide information about the process ambient during growth and have been used for processdriven closed-loop control of deposition rates 18 and epilayer composition 19 in molecular beam epitaxy, and more recently of the partial pressure of reactant species in a plasma-enhanced chemical vapor deposition reactor.…”

Real-time multivariable control of PECVD silicon nitride film properties

“…Zhou et al used the related technique of emission Fourier transform infrared spectrometry to measure the thickness of an epitaxial layer during growth [6]. Single-variable closed-loop control based on a wafer state sensor was implemented by Aspnes et al, who used an ellipsometer to control the aluminum concentration of a GaAlAs epitaxial layer [7]. Measurement of the concentrations or fluxes of chemical species requires process state sensors.…”

In situ monitoring of La0.67Sr0.33MnO3 monolayers grown by pulsed laser deposition

“…Even though this technique is particularly efficient for the early stage of the growth of thin layers up to a few tens of monolayers, direct evaluation of the oxidation state is not possible. Optical methods such as spectral ellipsometry [4][5][6], reflectance difference spectroscopy (RDS) [7][8][9][10][11][12], p-polarized reflection spectroscopy (PRS) [13][14][15][16], and laser light scattering [17,18], have demonstrated their abilities in monitoring film thickness, optical properties, chemical composition, and surface structures. In the meantime an original approach has been suggested and applied by Zhu and coworkers [19] to monitor the homo-and more recently heteroepitaxial growth of perovskites deposited on single substrates of SrTiO 3 .…”