g-CuCl is a wide-band gap (E g ¼ 3:395 eV at 4 K), direct band gap, semiconductor material with a cubic zincblende lattice structure. A very large exciton binding energy (190 meV), assures efficient exciton-based emission at room temperature. Its lattice constant, a CuCl ¼ 0:541 nm means that the lattice mismatch to Si (a Si ¼ 0:543 nm) is o0.5%.g-CuCl on Si-the growth of a wide-band gap, direct band gap, optoelectronics material on silicon substrate is a novel material system, with compatibility to current Si-based electronic/optoelectronics technologies. Both n-type and p-type CuCl will be required for development of homojunction light-emitting diodes (LEDs). The authors report on the impact of incorporation of Zn for n-type doping of CuCl by co-evaporation of CuCl and ZnCl 2 .Polycrystalline Zn-doped g-CuCl thin films are grown on Si (1 1 1), Si (1 0 0), and glass substrates by physical vapour deposition. X-ray diffraction (XRD) studies confirm that this n-doped CuCl has a cubic zincblende structure with a preferred (1 1 1) orientation. Several excitonic bands are evident in low-temperature photoluminescence (PL) measurements such as the Z 3 free exciton at $388 nm; I 1 -bound exciton at $392 nm and M free biexciton at $393 nm. Cathodoluminescence (CL) and PL reveal a strong room temperature Z 3 excitonic emission at $385 nm. Electrical measurements indicate n-type conductivity with resistivity $34 Ocm. r

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We have probed the luminescence properties of a wide-band-gap, direct band-gap optoelectronic material, grown on closely lattice-matched silicon substrates, namely, ␥-CuCl on Si. This material system is compatible with current Si or GaAs-based electronic/optoelectronic technologies. Polycrystalline epitaxy of CuCl can be controlled such that it maintains an orientation similar to the underlying Si substrate. Importantly, chemical interactions between CuCl and Si are eliminated. Photoluminescence and cathodoluminescence results for CuCl, deposited on either Si ͑100͒ or Si ͑111͒, reveal a strong room-temperature Z 3 excitonic emission at ϳ387 nm. We have developed and demonstrated the room-temperature operation of an ultraviolet electroluminescent device fabricated by the growth of ␥-CuCl on Si. The application of an electrical potential difference across the device results in an electric field, which promotes light emission through hot-electron impact excitation of electron-hole pairs in the ␥-CuCl. Since the excitonic binding energy in this direct band-gap material is of the order of 190 meV at room temperature, the electron-hole recombination and subsequent light emission at ϳ380 and ϳ387 nm are mediated by excitonic effects.

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The creation of stable, highly conductive ultrashallow junctions in strained Si is a key requirement for future Si based devices. It is shown that in the presence of tensile strain, Sb becomes a strong contender to replace As as the dopant of choice due to advantages in junction depth, junction steepness, and crucially, sheet resistance. While 0.7% strain reduces resistance for both As and Sb, a result of enhanced electron mobility, the reduction is significantly larger for Sb due to an increase in donor activation. Differential Hall and secondary-ion mass spectroscopy measurements suggest this to be a consequence of a strain-induced Sb solubility enhancement following epitaxial regrowth, increasing Sb solubility in Si to levels approaching 10(21) cm(-3). Advantages in junction depth, junction steepness, and dopant activation make Sb an interesting alternative to As for ultrashallow doping in strain-engineered complementary metal-oxide semiconductor devices. (c) 2008 American Vacuum Society