Nanoscale assembly of silicon-like [Al(As1−xNx)]ySi

Abstract

Ab initio theoretical simulations of Al(As 1−x N x )Si 3 alloys, a new class of optoelectronic materials, confirm that these compounds are likely to be disordered via a mechanism that preserves the integrity of the constituent III-V-Si 3 tetrahedra but randomizes their orientation in the average diamond lattice of the compound. This type of disorder is consistent with experimental structural data and with the proposed growth mechanism for such alloys, according to which "III:V(SiH 3 ) 3 " intermediate complexes are formed in the gas phase from reactions between group-III atomic beams and V(SiH 3 ) 3 molecules, delivering the entire III-V-Si 3 tetrahedra to the growing film. Experimental optical studies of these Al(As 1−x N x )Si 3 alloys as well as more general [Al(As 1−x N x )] y Si 5−2y compounds grown on Si substrates were carried out using spectroscopic ellipsometry. The resulting dielectric functions are found to be similar to broadened versions of their counterparts in pure Si. This broadening may have important practical applications, particularly in photovoltaics, because it dramatically enhances the optical absorption of Si in the visible range of the electromagnetic spectrum. A critical point analysis reveals the existence of direct optical transitions at energies as low as 2.5 eV, well below the lowest direct absorption edge of Si at 3.3 eV. Such transitions are predicted theoretically for perfectly ordered III-V-Si 3 compounds, and the experimental results suggest that they are robust against tetrahedra orientational disorder.

Rational Design of Monocrystalline (InP)yGe5–2y/Ge/Si(100) Semiconductors: Synthesis and Optical Properties

“…The E 1 / E 1 + Δ 1 transitions in InP appear at substantially higher energies than in Ge (ref ), so that the downshift we observe implies a large quadratic term with a coefficient (bowing parameter) close to b = 2 eV. Such large bowing coefficients are in qualitative agreement with findings III–V–Si systems. , When the linear interpolation is applied to the lowest direct (Γ point in the diamond Brillouin zone) and indirect (L-point) gaps, we predict that the material becomes a direct gap semiconductor for x > 0.5, as seen in Figure . The predicted band gap value at the indirect-to-direct transition is E 0 ∼ 0.9 eV.…”

“…Such large bowing coefficients are in qualitative agreement with findings III−V−Si systems. 11,17 When the linear interpolation is applied to the lowest direct (Γ point in the diamond Brillouin zone) and indirect (L-point) gaps, we predict that the material becomes a direct gap semiconductor for x > 0.5, as seen in Figure 7. The predicted band gap value at the indirect-to-direct transition is E 0 ∼ 0.9 eV.…”

“…To date, this approach has been used to grow new compounds such as AlPSi 3 and AlAsSi 3 , as well as corresponding alloys Al(As 1– x P x )Si 3 , Al(As 1– x N x )Si 3 , and Al(P 1– x N x )Si 3 . More generally, we have shown that an even broader range of compositions Al(As,P,N) y Si 5–2 y is accessible, spanning stoichiometric phases ( y = 1) which represent the maximum concentration (40%) of isolated III–V pairs to highly diluted system approaching the Si limit ( y → 0). − This work has generated growing interest from both theoretical and experimental perspectives because these materials have been predicted to exhibit unique absorption properties in a wavelength range needed for dramatic efficiency gains for the next generation of Si-based photovoltaics. , …”

Synthesis and Characterization of Monocrystalline GaPSi3 and (GaP)y(Si)5–2y Phases with Diamond-like Structures via Epitaxy-Driven Reactions of Molecular Hydrides

“…The synthesis of AlPSi 3 was later extended to form (AlP) y (Si) 5–2 y derivatives with tunable Si concentrations beyond the 60% threshold of the parent structure . Quaternary analogues with compositions Al­(As 1– x P x )­Si 3 , Al­(As 1– x N x )­Si 3 , and [Al­(P 1– x N x )] y (Si) 5–2 y were also produced using the N­(SiH 3 ) 3 compound as the source of AlNSi 3 building blocks. , …”

“…4 Quaternary analogues with compositions Al-(As 1−x P x )Si 3 , Al(As 1−x N x )Si 3 , and [Al(P 1−x N x )] y (Si) 5−2y were also produced using the N(SiH 3 ) 3 compound as the source of AlNSi 3 building blocks. 5,6 An important aspect of the research was to develop purely CVD routes that do not rely on solid sources. This is because this technique is far more attractive for large-scale, highthroughput fabrication of technologically relevant materials and provides more degrees of freedom in the pursuit of novel phases with specifically designed bonding configurations.…”