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Arbitrary Composition Profiles by MBE Using Desorption Mass Spectrometry

Published online by Cambridge University Press:  22 February 2011

K.R. Evans ,
R. Kaspi ,
W.T. Cooley ,
C.R. Jones  and
J.S. Solomon
K.R. Evans
Affiliation:
Solid State Electronics Directorate, Wright Laboratory, Wright-Patterson AFB, OH 45433
R. Kaspi
Affiliation:
Solid State Electronics Directorate, Wright Laboratory, Wright-Patterson AFB, OH 45433
W.T. Cooley
Affiliation:
Solid State Electronics Directorate, Wright Laboratory, Wright-Patterson AFB, OH 45433
C.R. Jones
Affiliation:
Technology Scientific Services, 3821 Colonel Glenn Hwy, Beavercreek, OH 45431
J.S. Solomon
Affiliation:
University of Dayton Research Institute, 300 College Park, Dayton, OH 45469
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Abstract

The ability to produce semiconductor structures with arbitrary vertical composition profiles offers the device physicist new freedom in device structure design. We report on the incorporation of the in-situ sensor technique of desorption mass spectrometry (DMS) in a realtime feedback loop for the continuous control of desorption rates. Assuming previous knowledge of relevant incident fluxes, this technique provides for continuous determination of the composition of the outermost layer of the growing crystal. Using AlGaAs growth as an example, the Ga desorption rate Fd(Ga) is monitored continuously during growth, providing an accurate measure of Al-fraction in the topmost layer of the growing film. By comparing the measured and desired Fd(Ga), an error signal is generated and minimized by varying an appropriate growth parameter. Structures which are vertically graded in composition are produced by programming a varying Fd(Ga) versus time profile. Both substrate temperature Ts and incident arsenic flux Fi(As2) affect Fd(Ga) in a controllable way. Thus, two distinct control loops are constructed based on variable Ts and Fi(As2), respectively. As demonstration vehicles, graded AlGaAs structures with linear, parabolic, sawtooth, and sinusoidal compositional profiles have been produced and characterized. Additionally, we discuss some of the limitations of this technique and its applicability to other materials.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 300: Symposium D1 – III-V Electronic and Photonic Device Fabrication and Performance , 1993 , 495
Copyright
Copyright © Materials Research Society 1993

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References

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