Kinetic Analysis of Surface Adsorption Layer in GaAs(001) Metalorganic Vapor Phase Epitaxy by In situ Reflectance Anisotropy Spectroscopy

Abstract

A kinetic analysis of the surface adsorption layer of III/V semiconductors in metalorganic vapor phase epitaxy (MOVPE) was carried out by monitoring the temporal behavior of surface reconstruction that is assumed to be maintained during growth with the adsorption layers. A GaAs(001) surface was observed in situ using reflectance anisotropy spectroscopy (RAS), and both spectroscopic and kinetic analyses were performed when trimethylgallium (TMGa) was supplied intermittently while the supply of tertiarybutylarsine (TBAs) was continuous. When the flow of TMGa was switched on/off, the transient RA signal exhibited time constants of 0.2 -20 s. By observing the dependence of these time constants on the partial pressure of TMGa and substrate temperature, we considered that the time constant (t 0 ) at the start of TMGa supply corresponds to the adsorption of Ga from the gas phase to the adsorption layer, and two constants (i.e., t 1 and t 2 ) at the end of TMGa supply are associated with the crystallization of adsorbed Ga and the recovery of surface reconstruction, respectively. The equivalent thickness of the adsorption layer was estimated to be 0.19 monolayer thickness at 550 C.

Kinetic analysis of surface adsorption layer for InGaAsP-related binary materials using in situ RAS

“…3. The values of t 0 are close to the detection limit of the RAS system (0.270.1 s) according to our previous work [3], and we have to expect a substantial error range. However, it can be supposed that t 0 corresponds to the adsorption, because the rate of adsorption, 1/t 0 , increased linearly with the partial pressure of group-III precursors.…”

“…The reciprocal value of this time constant t 1 represents the incorporation rate constant of adsorbed group-III atoms. It has been already confirmed that these time constants are not affected by the gas-phase phenomena, as described in our previous report [3].…”

“…Above all, focus was made on the behavior of group-III atoms. In our previous study [3], the adsorption layer on a GaAs(0 0 1) surface was observed. Time constants regarding the generation or extinction of the adsorption layer were extracted, and their dependence on the surface temperature and partial pressure of the Ga source was examined, which led to the following conclusions: (1) -CH 3 groups are not present on GaAs surfaces at growth temperatures higher than 500 1C, thus it is certain that only time constants regarding surface reactions of Ga atoms were observed.…”

“…During the supply of the group-III sources, gas-phase precursors and/or intermediates containing -CH 3 dissociatively on the growth surface to yield group-III atoms in the adsorption layer, which affects the kind of surface reconstruction and/or the fraction of the reconstructed atoms, and can thus be detected as a change in the RA signal. Typical time transients of the RA signal are shown in Fig.…”

In Situ Characterization of Interfaces Relevant for Efficient Photoinduced Reactions

“…Surface reconstructions similar to those known from UHV studies were found to occur also for MOVPE preparation in various process gases, but, in general, surface reactions are more complex in MOVPE ambient . In particular, surface reactions play a crucial role during initiation of GaAs homoepitaxy …”