Properties of boron-doped μc-Ge:H films deposited by hot-wire CVD

Abstract

Boron-doped hydrogenated microcrystalline Germanium (μc-Ge:H) films were deposited by hot-wire CVD. H₂ diluted GeH₄ and B₂H₆ were used as precursors and the substrate temperature was kept at 300 °C. The properties of the samples were analyzed by XRD, Raman spectroscopy, Fourier transform infrared spectrometer and Hall Effect measurement with Van der Pauw method. It is found that the films are partially crystallized, with crystalline fractions larger than 45% and grain sizes smaller than 50 nm. The B-doping can enhance the crystallization but reduce the grain sizes, and also enhance the preferential growth of Ge (220). The conductivity of the films increases and tends to be saturated with increasing diborane-to-germane ratio $R_{B_2 H_6 } $. All the Hall mobilities of the samples are larger than 3.8 cm²·V⁻¹·s⁻¹. A high conductivity of 41.3 Ω⁻¹·cm⁻¹ is gained at $R_{B_2 H_6 } $=6.7%.

Keywords

Boron / μc-Ge:H film / HWCVD / crystalline fraction / conductivity / Hall mobility

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