III-V OMVPE growth and characterisation of graded AlₓGaₓ₋₁As-GaAs layers and heterointerfaces for the development of GRIN-SCH lasers and Gunn diodes
Master Thesis
1994
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University of Cape Town
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Abstract
AlGaAs-GaAs graded index single confinement heterostructure single quantum well
(GRIN-SCH SQW) lasers and both 35 GHz and 94 GHz Gunn diodes have been
satisfactorily grown by organometallic vapour phase epitaxy (OMVPE). This work is
based on the material development of such device structures and systematically shows
the steps taken to achieve the final goal of repeatedly producing high quality devices
geared towards small-scale production. The key elements of the process are the
realisation of high quality AlGaAs compositionally graded layers, abrupt GaAs-AlGaAs
as well as dopant heterointerfaces and silicon-dopant spikes.
A consistently high quality of epitaxial GaAs and AlGaAs is achievable with controllable
silicon, tellurium and zinc doping on both material systems. The OMVPE system is
sufficiently calibrated to grow sharp transitions in GaAs doping interfaces and quantum
wells in the order of 2.5 nm. SIMS measurements showed almost square doping profiles
in the 35 GHz Gunn diode structure and was able to resolve a 5 nm Si-spike doping
layer in GaAs. The SIMS results of the 94 GHz Gunn diode material clearly indicates
the presence of all layers with certain measured values evolving exactly as designed.
These achievements are attributed to the fine pressure and flow control implemented on
the reactor system by using automated steps to control the growth process.
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Bibliography: pages 125-131.
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Reference:
Thavar, R. 1994. III-V OMVPE growth and characterisation of graded AlₓGaₓ₋₁As-GaAs layers and heterointerfaces for the development of GRIN-SCH lasers and Gunn diodes. University of Cape Town.