The surface chemistry of GaAs atomic layer epitaxy
In this paper we review three proposed mechanisms for GaAs ALE and review or present data support or contradiction of these mechanisms. Surface chemistry results clearly demonstrated that TMGa irreversibly chemisorbs on the Ga-rich GaAs(100) surface. The reactive sticking coefficient (RSC) of TMGa on the adsorbate-free Ga-rich GaAs(100) surface was measured to be {approximately}0.5, conclusively demonstrating that the selective adsorption'' mechanism of ALE is not valid. We describe kinetic evidence for methyl radical desorption in support of the adsorbate inhibition'' mechanism. The methyl radical desorption rates determined by temperature programmed desorption (TPD) demonstrate that desorption is at least a factor of {approximately}10 faster from the As-rich c(2 {times} 8)/(2 {times} 4) surface than from the Ga-rich surface. It is disparity in CH{sub 3} desorption rates between the As-rich and Ga-rich surfaces that is largely responsible for GaAs ALE behavior. A gallium alkyl radical (e.g. MMGa) is also observed during TPD and molecular beam experiments, in partial support of the flux balance'' mechanism. Stoichiometry issues of ALE are also discussed. We have discovered that arsine exposures typical of atmospheric pressure and reduced pressure ALE lead to As coverages {ge} 1 ML, which provides the likely solution to the stoichiometry question regarding the arsine cycle. 32 refs., 6 figs.
- Research Organization:
- Sandia National Labs., Albuquerque, NM (USA)
- Sponsoring Organization:
- DOE; USDOE, Washington, DC (USA)
- DOE Contract Number:
- AC04-76DP00789
- OSTI ID:
- 5620165
- Report Number(s):
- SAND-90-3130C; CONF-910406--20; ON: DE91014112
- Country of Publication:
- United States
- Language:
- English
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360603* -- Materials-- Properties
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400201 -- Chemical & Physicochemical Properties
ALKYL RADICALS
ARSENIC COMPOUNDS
ARSENIDES
CHEMICAL COATING
CHEMICAL REACTION KINETICS
CHEMICAL REACTIONS
CHEMICAL VAPOR DEPOSITION
CHEMISORPTION
DEPOSITION
DESORPTION
EPITAXY
GALLIUM ARSENIDES
GALLIUM COMPOUNDS
KINETICS
METHYL RADICALS
NATIONAL ORGANIZATIONS
ORGANIC COMPOUNDS
ORGANOMETALLIC COMPOUNDS
PNICTIDES
RADICALS
REACTION KINETICS
SANDIA LABORATORIES
SEPARATION PROCESSES
SORPTION
SURFACE COATING
SURFACE PROPERTIES
US AEC
US DOE
US ERDA
US ORGANIZATIONS
VAPOR PHASE EPITAXY