Thermodynamic analysis of anion exchange during heteroepitaxy

Abstract

A thermodynamic approach is presented to assess the extent of anion exchange reactions during the heteroepitaxy (molecular beam epitaxy) of dissimilar anion III-V compound semiconductor structures. It is shown that the extent of anion exchange can be predicted by the change in the Gibbs free energy. Bond strength changes can only be used as a guide in comparing the relative tendency for exchange, rather than as a criterion. The driving force for anion exchange strongly depends on the conditions during interface formation. A number of important factors, including bond strength, misfit strain energy, surface structure and energy, the equilibrium between dimers V 2 and tetramers V 4 , and segregation are discussed in terms of their contributions to the thermodynamics. r

Formation of interfacial misfit dislocation in GaSb/GaAs heteroepitaxy via anion exchange process

“…In this step, the samples were soaked under constant Sb flux at their respective T sub for 4 min. Under a constant supply of Sb flux, As atoms on the surface of GaAs was replaced by a single monolayer of Sb atoms via anion exchange process [16]. In the anion exchange process, Ga-As bonds on the surface of the GaAs was reacted with the incoming Sb atoms to form Ga-Sb bonds.…”

Effect of dissimilar anion annealing on structures of InAs/GaAs quantum dots

“…This anion exchange has been predicted to be favorable thermodynamically under typical epitaxial conditions [26]. As a result of the P-forAs anion exchange, a ternary InAs x P (1Àx) alloy layer is formed in the topmost surface of the dot layer, and the coherent strain energy, the driving force for the 2D-to-3D growth, is reduced due to the smaller lattice-mismatch.…”

Lateral compositional modulation in lattice-matched GaInP/GaAs heterostructures

“…This phenomenon is believed to be related to the interplay of compositional modulation and dislocations and will be reported elsewhere. 19 Unlike the (002) reflection, of which the scattering structure factor is sensitive to chemical composition, the (004) two-beam diffracting condition cannot be used to differentiate epilayers even though the chemical composition differs considerably, because its structure factor does not strongly depend on chemical composition. For comparison, a (004) DFI of the heterostructure is shown in Fig.…”