CBE Growth Characterization of GaAs and InGaAs by Rheed and RD
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CBE GROWTH CHARACTERIZATION OF GaAs AND InGaAs BY RHEED AND RD G. PAULSSON, B. JUNNO AND L. SAMUELSON Department of Solid State Physics, Lund University, P. 0. Box 118, S-221 00 Lund, Sweden ABSTRACT Triethylgallium, trimethylindium and tertiarybutylarsine have been used to grow GaAs and InGaAs on (001)GaAs. No pre-cracking was used so that the thermal decomposition of tertiarybutylarsine on GaAs could be studied. The growth has been monitored in-situ using reflection high-energy electron diffraction and reflectance-difference. A comparison is made between the reflectance difference signal and the intensity of the reflection high-energy electron diffraction specular spot as the surface is transformed from As rich to Ga rich. Using the former technique similar growth transients have also been studied as a function of the temperature. It is found that the incorporation of small amounts of In (less than 5 per cent) in the buffer layer significantly improves the oscillatory behavior of the RD-signal when growth of GaAs is commenced. Finally, the growth dynamics of InGaAs is studied using reflection high-energy electron diffraction. INTRODUCTION The great importance of organometallic based epitaxy for the growth of III-V materials has stimulated the development of new powerful in-situ measurement techniques. The recently introduced technique of reflectancedifference (RD) is now already well established and is used in high vacuum (HV) techniques such as molecular beam epitaxy (MBE) and chemical beam epitaxy (CBE) in parallel with reflection high-energy electron diffraction (RHEED) to provide further information on the surface chemical processes. Since RD is an optical technique it has also been used to bridge the knowledge gap between HV techniques and techniques using a total pressure too high for the employment of RHEED. These investigations show that the surface conditions indeed are very similar even for the two extremes, HV and atmospheric pressure conditions. In this paper, we study the growth of GaAs and InGaAs on (001)GaAs using RHEED and RD. First we describe the CBE apparatus including the gas injection system used in these investigations. Then we give the temperature dependence of the temporal evolution of the RD response as the surface is transformed from As rich to Ga rich conditions and vice versa. For a single temperature such a growth transient is also studied by RD and RHEED specular spot measurements. We then show how the incorporation of a small amount of In, less than 5 per cent, in the buffer layer significantly improves the RD growth oscillations. Finally, the growth kinetics have been studied for InGaAs on (001)GaAs by the use of RHEED.
Mat. Res. Soc. Symp. Proc. Vol. 282. 01993 Materials Research Society
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EXPERIMENTAL PROCEDURE The CBE apparatus These experiments were performed in a custom made compact ultra high vacuum (UHV) chamber equipped with a liquid nitrogen cryo-shroud and is described in detail elsewhere [1]. The gas injection system is designed to allow abrupt gas switching in the
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