An enhancement of computer performance following Moore’s law requires the miniaturization of semiconductor devices. Presently, their dimensions reach the nanoscale. Interfaces between materials become increasingly important as the volume is reduced. It is shown here how a pyramidal interface structure is formed irrespective of the conditions applied during the growth of two semiconductors. This drastically changes the common view of interfaces, which were assumed to be either atomically abrupt or interdiffused. Especially in semiconductor heteroepitaxy, a simple surface segregation of one atomic species is often assumed. It is proven by first-principles computations and kinetic modeling that the atom mobility during growth and the chemical environment at the interface are the decisive factors in the formation of the actual structure. Gallium phosphide grown on silicon was chosen as representative, nearly unstrained material combination to study the fundamental parameters influencing the interface morphology. Beyond that, this system has significant impact for cutting-edge electronic and optoelectronic devices. The findings derived in this study can be generalized to aid the understanding of further relevant semiconductor interfaces. This knowledge is crucial to comprehend current and steer future properties of miniaturized devices.

Alkylboranes, such as trimethylboron (TMB) and triethylboron (TEB), are promising alternative precursors in lowtemperature chemical vapor deposition (CVD) of boron-containing thin films. In this study, CVD growth of B−C films using TMB and quantum-chemical calculations to elucidate a gas phase chemical mechanism were undertaken. Dense, amorphous, boron-rich (B/C = 1.5−3) films were deposited at 1000 °C in both dihydrogen and argon ambients, while films with crystalline B 4 C and B 25 C inclusions were deposited at 1100 °C in dihydrogen. A script-based automatization scheme was implemented for the quantum-chemical computations to enable time efficient screening of thousands of possible gas phase CVD reactions. The quantum-chemical calculations suggest TMB is mainly decomposed by an unimolecular α-H elimination of methane, which is complemented by dihydrogen-assisted elimination of methane in dihydrogen.

The gas phase decomposition reactions of precursor molecules relevant for metal-organic vapour phase epitaxy (MOVPE) of semiconductor thin films are investigated by computational methods on the density-functional level as well as on the ab initio (MP2, CCSD(T)) level. A comprehensive reaction catalogue of uni- and bimolecular reactions is presented for triethylgallium (TEG) as well as for tert-butylphosphine (TBP) containing thermodynamic data together with transition state energies. From these energies it can be concluded that TEG is decomposed in the gas phase under MOVPE conditions (T = 400-675 °C, p = 0.05 atm) to GaH3via a series of β-hydride elimination reactions. For elevated temperatures, further decomposition to GaH is thermodynamically accessible. In the case of TBP, the original precursor molecule will be most abundant since all reaction channels exhibit either large barriers or unfavorable thermodynamics. Dispersion-corrected density functional calculations (PBE-D3) provide an accurate description of the reactions investigated in comparison to high level CCSD(T) calculations serving as benchmark values.

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