GaAs 1−x Bi x epilayers with bismuth concentrations up to x=3.1% were grown on GaAs by molecular beam epitaxy. The Bi content in the films was measured by Rutherford backscattering spectroscopy. X-ray diffraction shows that GaAsBi is pseudomorphically strained to GaAs but that some structural disorder is present in the thick films. The extrapolation of the lattice constant of GaAsBi to the hypothetical zincblende GaBi alloy gives 6.33±0.06 Å. Room-temperature photoluminescence of the GaAsBi epilayers is obtained and a significant redshift in the emission of GaAsBi of ∼84 meV per percent Bi is observed.

The band gap of GaAsBi epitaxial layers as a function of bismuth concentration up to 3.6% is determined. The optical transitions were measured by modulated electroreflectance. The energy of the band gap decreases at a linearized rate of 88 meV/% Bi, or 83 meV/% Bi for the heavy hole to conduction band transition for GaAsBi strained to GaAs. The valence-band splitting increases faster than that of GaAs under similar compressive strain whereas the temperature dependence of the observed GaAsBi transitions is similar to that of GaAs.

We report a giant bowing of the spin-orbit splitting energy Delta0 in the dilute GaAs1-xBix alloy for Bi concentrations ranging from 0% to 1.8%. This is the first observation of a large relativistic correction to the host electronic band structure induced by just a few percent of isoelectronic doping in a semiconductor material. It opens up the possibility of tailoring the spin-orbit splitting in semiconductors for spintronic applications.

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In an effort to make semiconductor nanomaterials with tunable properties, we have deliberately designed and synthesized a family of novel organic-inorganic hybrid nanocomposites based on II-VI semiconductors with structures ranging from one-dimensional (1-D) chain to two-dimensional layer (2-D) to three-dimensional (3-D) framework. All nanostructures exhibit strong quantum confinement effect (QCE), while possessing a perfectly periodic arrangement. The optical absorption experiments show that all compounds generate a very large blue shift in the absorption edge (1.0-2.0 eV) due to the strong QCE. More significantly, their band edge shift and optical properties can be tuned by changing the dimensionality of inorganic motifs as well as overall crystal structures. Raman studies reveal that not only do these structures have distinctly different vibrational signatures from those of the II-VI host semiconductors, but they also differ significantly from each other as a result of changes in dimensionality. The crystal structures of these nanocomposite materials have been characterized by single crystal and/or powder X-ray diffraction methods. [ZnTe(pda)] (1; pda = propanediamine) is composed of 1-D chains of [ZnTe] with pda chelating to Zn atoms. [ZnTe(N(2)H(4))] (2; N(2)H(4) = hydrazine) and [ZnTe(ma)] (3; ma = MeNH(2) = methylamine) are two-dimensional (2-D) layered structures containing [ZnTe] slabs and terminal hydrazine (2) or methylamine (3) molecules. The crystal structures of [CdSe(en)(0.5)] (4; en = ethylenediamine) and [CdSe(pda)(0.5)] (5) are 3-D networks containing [CdSe] slabs bridged by bidentate organic diamine molecules. Crystal data for 1: Orthorhombic, space group Pbcm, a = 9.997(2), b = 6.997(1), c = 10.332(2) A, Z = 4. For 2: Monoclinic, space group P2(1), a = 4.2222(6), b = 6.9057(9), c = 7.3031(10) A, beta = 98.92(8) degrees, Z = 2. For 3: Orthorhombic, Pbca, a = 7.179(1), b = 6.946(1), c = 18.913(4) A, Z = 8. For 4: Orthorhombic, Pbca, a = 7.0949(3), b = 6.795(3), c = 16.7212(8) A, Z = 8. For 5: Orthorhombic, Cmc2(1), a = 20.6660(12), b = 6.8900(4), c = 6.7513(4) A, Z = 8.