Kinetic model of element III segregation during molecular beam epitaxy of III-III′-V semiconductor compounds

Abstract

Segregation of column III atoms during molecular beam epitaxy of III-III′-V semiconductor compounds causes nonabrupt interfaces and a surface composition different from the bulk one. To derive concentration profiles, a thermodynamical equilibrium model has been used for a long time. This model applies well to describe segregation processes at high growth temperatures, but fails in predicting concentration profile variations with substrate temperature. We have thus developed a kinetic model which correctly takes into account the evolution with the growth temperature. We apply this model to the case of indium segregation in the GaxIn1−xAs/GaAs system. The calculated indium concentration profiles are compared to those obtained with the thermodynamical equilibrium model. A kinetic limitation of segregation is shown to appear at low substrate temperatures and sufficiently high growth rates. This limitation is predicted to arise below 400 °C for a growth rate of 1 monolayer/s for In segregation in the GaxIn1−xAs/GaAs system.

How kinetics drives the two- to three-dimensional transition in semiconductor strained heterostructures: The case of InAs∕GaAs(001)

“…In accordance with the model proposed by Dehaese et al, [32] at 1.45 ML the average concentration of In in the uppermost layer is certainly greater than 82%. [8] However, our data clearly show that the nucleation is preferential at the step edges, an occurrence which we highlight further.…”

Role of segregation in InAs/GaAs quantum dot structures capped with a GaAsSb strain-reduction layer

“…At the same time a more chemically justified model of segregation, initially verified for SiGe alloys, was presented by Fukatsu et al 71 and Fujita et al 72 The same method, known generally as the kinetic model of segregation, was extended to exchanges of group III atoms in III-V alloys by Dehaese et al 73 In the kinetic model of segregation the process of diffusion is assumed to occur only between the growing layer and the one immediately below while all the other layers ͑bulk͒ are considered to be frozen. The evolution of the number of In surface atoms is given by the balance of incoming and leaving In or Ga atoms,…”

“…The previous models of segregation are based on the twostate exchange 70,71,73 mechanism, where only atomic exchange among the subsurface and surface states is considered. Godbey and Ancona 75 instead proposed to extend the kinetic model to a three-layer exchange mechanism.…”

“…44,73 A variant of the kinetic method is the so-called thermodynamic model and was originally proposed by Moison et al 74 The governing equations are obtained from the kinetic model equations assuming high temperature. Under this condition the stationary state is well described by the condition of absence of impinging flux, which reduces Eq.…”

Formation of InAs wetting layers studied by cross-sectional scanning tunneling microscopy

“…Several models for indium segregation have been proposed. [7][8][9][10] We use the phenomenological model of Muraki et al, 8 which has been shown to describe the indium composition x͑n͒ of InAs WLs well: 3…”