Paul Fons

Growth and characterization of CuInSe{sub 2} epitaxial films for device applications

CuInSe{sub 2} (CIS) epitaxial layers have been grown on both GaAs (001) and In{sub 0.29}Ga{sub 0.71}As pseudo lattice-matched substrates by molecular beam epitaxy, and characterized for device applications. Despite a large lattice mismatch of {Delta}a/a{approximately}2.2%, epitaxial growth of CuInSe{sub 2} has been demonstrated on GaAs (001) showing their film properties strongly dependent on the Cu/In ratio. In-rich films had a large number of twins on {l_brace}112{r_brace} planes, and were found to be heavily compensated. On the other hand, Cu-rich films showed distinct photoluminescence emissions indicating significantly higher film quality in comparison with In-rich films. Two dimensional reciprocal x-ray intensity area mapping and cross-sectional transmission electron microscopy showed the formation of an interfacial layer in the vicinity of the CuInSe{sub 2}/GaAs interface resulting from the strain-induced interdiffusion between CuInSe{sub 2} and GaAs. Reduction in lattice mismatch to {Delta}a/a{approximately}0.2% by using In{sub 0.29}Ga{sub 0.71}As pseudo lattice-matched substrates made possible the growth of high quality CuInSe{sub 2} with predominant free exciton emissions in their photoluminescence spectra and with residual defect densities of as low as p {approximately} 1 {times} 10{sup 17}cm{sup {minus}3} implying the growth of device quality CuInSe{sub 2} epitaxial films.

The effects of air annealing on CuInSe{sub 2} thin films grown by molecular beam epitaxy

High quality epitaxial CuInSe{sub 2} (CIS) films with a range of Cu/In ratios ({gamma}) = 0.80--2.24 grown by molecular beam epitaxy (MBE) have been post-annealed at temperatures of T{sub A} = 200--400 C in both dry-air and Ar atmospheres. Changes in the structure and composition due to annealing have been investigated. The only oxide observed experimentally for both the In-rich, and the Cu-rich CIS films was In{sub 2}O{sub 3}. This is consistent with equilibrium thermodynamic calculations which indicate that In{sub 2}O{sub 3} is the most stable solid oxide phase. During annealing some reactions are probably kinetically limited making the annealing process a function of time and temperature, but the equilibrium thermodynamic results reported here simplify interpretation of phase space.

In-situ Subplantation of Low-Energy (~100 eV) C+ into GaAs using Combined Ion Beam and Molecular Beam Epitaxy

A combined ion beam and molecular beam epitaxy (CIBMBE) system has been developed. In this technique an ion implanter capable of impinging ions with energies of 30 eV–30 keV is connected to a conventional MBE system under ultra-high vacuum (UHV) conditions. This system can independently control mass, current and energy of a variety of ion beams. As a successful application of CIBMBE, 100 eV carbon ions (C + ) have been incorporated into growing MBE GaAs layers. Van der Pauw and photoluminescence (PL) measurements indicate that C atoms are efficiently introduced as acceptors and radiation damages are not significantly produced.