Suppression of In surface segregation and growth of modulation-doped N-AlGaAs/InGaAs/GaAs structures with a high In composition by molecular-beam epitaxy

Abstract

A model is proposed for describing the origin of the growth mode transition from two to three dimensions during the molecular-beam epitaxial growth of InGaAs on GaAs [H. Toyoshima, T. Niwa, J. Yamazaki, and A. Okamoto, Appl. Phys. Lett. 63, 821 (1993)]. In this model the amount of In atoms on the surface arising from surface segregation is crucial in determining the growth mode transition, which provides the upper limit of the In composition and/or the thickness of InGaAs for device applications. The increase of these limited values for a modulation-doped structure with an InGaAs channel has been implemented on the basis of this model. A lower substrate temperature and a higher As4 pressure during the InGaAs growth greatly suppress the In segregation ratio leading to the decrease of the amount of In on the surface. These growth conditions enable the upper limit of the In composition and/or the critical thickness of the InGaAs channel to be increased, which further verifies the validity of the proposed model. The surface of the InGaAs with the higher In composition is, however, metastable and can be stabilized by depositing AlGaAs or GaAs more than 3 monolayers thick on it. Modulation-doped structures with high electron transport properties have been successfully grown as high as the In composition of 0.45 by controlling the growth kinetics of InGaAs.

Growth of highly strained InGaAs quantum wells on GaAs substrates—effect of growth rate

“…To achieve this, three main growth parameters, i.e. low growth temperature, high V/III ratio and high growth rate, have been identified [15][16][17][18][19]. However, in this work we shall present results from our growth studies by metal organic vapor-phase epitaxy (MOVPE) that extremely low growth rate at low temperature favored a high-quality QW with very smooth surface, in contradiction to previous reports [15,16].…”

Surface chemistry evolution during molecular beam epitaxy growth of InGaAs

“…This trend with T s agrees well with previous reports. 2,8 Thermodynamic equilibrium arguments suggest that ⌰ In,ss should decrease with increasing growth temperature: the overall segregation process is associated with decreases in both enthalpy and entropy. Thus, kinetic limitations are present, and the data are well described by a local equilibrium model in which only the outermost region of the crystal participates in the segregation process.…”

“…1,9 Other reports on the effect of the V/III ratio used a tetrameric arsenic source and reached conflicting results regarding the effect of the V/III ratio on the surface-segregation process. 1,8 The tendency of the surface-segregated indium atoms to penetrate into the GaAs cap was probed by performing TPD analyses on 24.25 ML InGaAs covered by GaAs caps of varying thickness, all grown at T s ϭ530°C. ͑Similar data for T s ϭ480°C were not acquired.͒ The results are shown in Fig.…”

The role of the surface adsorption layer during MOVPE growth analyzed by the flow modulation method

“…The segregation of In atoms at the top of an epitaxial film is one example. In this segregation phenomenon, despite the fact that In-and Ga-containing ternary compounds such as InGaP [4], InGaAs [5], InGaN [6,7] are grown using constant ratios of the source gases over time, Ga-rich layer is formed at the bottom of the film, whereas an In-rich layer is formed at the top due to the segregation of the In atoms. In particular, in the pseudomorphic growth of InGaAs/GaAs or InGaN/GaN, the noticeable lattice mismatch is considered to cause segregation, yet such segregation phenomenon has also been observed in lattice-matched InGaP/GaAs.…”