Pulsed laser deposition and thin film properties of p-type barium copper sulfur fluoride, barium copper selenium fluoride, barium copper tellurium fluoride and n-type zinc indium oxide wide band-gap semiconductors

Thin films of wide band-gap semiconductors are deposited by the pulsed laser deposition method. Optimal deposition parameters for the individual compounds are reported. A family of p-type BaCuQF (Q = S, Se, Te) ceramics with a layered crystalline structure is investigated for active and passive device applications. Epitaxial films of BaCuTeF are grown in-situ on single-crystal MgO substrates. These films exhibit a maximum hole mobility of 8 cm2/Vs and conductivity of 167 S/cm. The band gap of BaCuTeF is 3 eV, much higher than 2.3 eV expected from powder results. BaCuSeF textured films are also grown on MgO substrates with a lower 1.5 cm2/Vs and 1.7 x 1018 cm -3 carrier concentration. Crystalline films of BaCuSF are obtained by post-annealing in H2S and Ar gases. Excitonic absorptions above 3 eV in BaCuSeF and BaCuSF indicate the upper limit of photon transmission. Various photoluminescence colors in the visible range are observed under UV excitation. The Zn2In2O5 (ZIO) is also a layered semiconductor, but with electron majority carrier-type. Amorphous and crystalline ZIO films have 2 x 103 S/cm conductivity and indirect band gaps between 2.8 and 3.2 eV, respectively. The amorphous phase is stable to high temperature exposure up to 500°C.