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Orientation selective effects in III-V heterostructure systems with application to nanostructure fabrication


Hoenk, Michael Eugene (1990) Orientation selective effects in III-V heterostructure systems with application to nanostructure fabrication. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/ppm7-sq27.


Orientation selective effects in the molecular beam epitaxial (MBE) growth of Al1-xGaxAs on a patterned (100) GaAs substrate are investigated. Under particular growth conditions, the spontaneous, selective formation of a superlattice or quantum wire array on the sides of grooves is observed. Experiments and modelling indicate that this growth technique, orientation selective epitaxy (OSE), has application to the in situ growth of manometer scale structures.

An optical fiber cathodoluminescence system is described. By using an optical fiber to collect light directly from the surface of the sample, spectrally resolved cathodoluminescence measurements can be done without precluding simultaneous measurement of other signals. The system attains comparable performance to alternative systems which utilize concave mirrors for light collection. A cryogenic cold stage, using a continuous flow of liquid helium or nitrogen, is described.

Experimental results on the MBE growth of AlxGa1-xAs on [011] grooves in a (100) GaAs substrate exhibit orientation selective effects. Spontaneous growth of a superlattice is observed on the sides of grooves. The superlattice, with a period of approximately 70A, exhibits strong luminescence, red-shifted by 127 meV from the emission of uniform Al0.25Ga0.75As grown on adjacent facets. This is the first observation of compositional modulation in the growth of AlGaAs on a {111} surface. The abrupt termination of the superlattice at the interface with adjacent facets constitutes a heterojunction oriented lateral to the growth direction, the first such structure to be formed spontaneously during growth.

Orientation selective epitaxy is modelled, using calculations and Monte Carlo simulations of growth on surfaces inclined with respect to the substrate rotation axis. The proposed mechanism predicts an in-plane variation of the composition, resulting from growth by step flow in the presence of time dependent fluxes. The time dependence is caused by the inclination of the surface with respect to the substrate rotation axis.

The dependence of OSE growth on surface orientation is investigated by varying groove orientation in a patterned (100) GaAs substrate. A strong dependence of cathodoluminescence emission on groove orientation is observed. In some ranges of groove angles, monotonic dependence of the peak emission on groove orientation is observed, suggesting the possibility of bandgap tuning by variation of surface orientation. In growth on [010] grooves, quantum wire arrays were observed, with a wire dimension of approximately 60A.

The growth of AlxGa1-xAs in oval defects is investigated. A strong dependence of the composition on the orientation of growth in oval defects is observed. Comparison with growth in grooves indicates that orientation selective epitaxy plays a role in determining AlxGa1-xAs composition in oval defects.

Item Type:Thesis (Dissertation (Ph.D.))
Degree Grantor:California Institute of Technology
Division:Physics, Mathematics and Astronomy
Major Option:Physics
Thesis Availability:Public (worldwide access)
Research Advisor(s):
  • Vahala, Kerry J.
Thesis Committee:
  • Unknown, Unknown
Defense Date:15 May 1990
Record Number:CaltechETD:etd-06122007-091106
Persistent URL:
Default Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:2560
Deposited By: Imported from ETD-db
Deposited On:03 Jul 2007
Last Modified:16 Apr 2021 23:01

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PDF (Hoenk_me_1990.pdf) - Final Version
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