Competitive Kinetics Model to Explain Surface Segregation of Indium during InGaP Growth by Using Metal Organic Vapor Phase Epitaxy

Abstract

An InGaP layer grown by metal organic vapor phase epitaxy (MOVPE) often has an In-rich region within 5 nm from the top of the layer. This surface segregation degrades the interface abruptness of InGaP/GaAs systems, which is attractive for high-performance devices such as high electron mobility transistors (HEMTs). This segregation in lattice-matched InGaP/GaAs systems can be explained by considering a ''subsurface'' in which a surface adsorption layer controls the composition of grown epitaxial layers. In this study, the existence of a subsurface during MOVPE growth of InGaP was experimentally confirmed through kinetic analysis involving a flow modulation method. The kinetic parameters of a subsurface model, such as adsorption and desorption rate constants of each species, were estimated based on experimental data obtained from flow modulation, and then used to successfully explain the In surface segregation in InGaP-MOVPE. #

Precise structure control of GaAs/InGaP hetero-interfaces using metal organic vapor phase epitaxy and its abruptness analyzed by STEM

“…(We previously developed this subsurface model and examined its accuracy in Refs. [19,22]). Based on our subsurface model, we developed three different methods to suppress In segregation: flow-rate change (Fig.…”

“…We previously developed an optimized gas-switching sequence to fabricate InGaP/GaAs hetero-structures with abrupt hetero-interfaces by MOVPE [17][18][19][20][21][22][23][24]. Two major issues exist in the fabrication of InGaP on GaAs (InGaP/GaAs) hetero-interfaces, which are listed as follows.…”

“…The most critical problem in GaAs/InGaP hetero-interface fabrication, however, is In segregation, which occurs due to excess In atoms in the top surface of InGaP during growth. During InGaP growth by MOVPE, an In segregation layer can exceed 10 mono-layers (MLs) [22][23][24], and thus causes the degradation of device properties such as effective carrier mobility due to scattering at the interface. We previously developed the ''subsurface'' model that explains In segregation, and has been proven experimentally [19,22].…”

“…During InGaP growth by MOVPE, an In segregation layer can exceed 10 mono-layers (MLs) [22][23][24], and thus causes the degradation of device properties such as effective carrier mobility due to scattering at the interface. We previously developed the ''subsurface'' model that explains In segregation, and has been proven experimentally [19,22]. In our subsurface model in MOVPE, the top surface atoms are in an unsteady state and thus are crystallized or desorbed according to the process operations [20][21][22].…”

“…We previously developed the ''subsurface'' model that explains In segregation, and has been proven experimentally [19,22]. In our subsurface model in MOVPE, the top surface atoms are in an unsteady state and thus are crystallized or desorbed according to the process operations [20][21][22]. The subsurface model revealed that In surface segregation is due to the imbalance in crystallization rates between the InP subsurface and GaP subsurface, thus resulting in In surface segregation in the remaining top surface layer of InGaP after epitaxial growth is terminated [22].…”