Influence of Temperature on the Distribution of Oxygen in Germanium Grown on Gallium Arsenide.

Abstract : The Fourier Transform infrared (FTIR) absorption spectrum from 500 to 4000/cm was measured for several Ge films deposited on GaAs using ultra high vacuum (UHV) E-beam deposition at substrate temperatures ranging from room temperature (RT) to 500 deg C. The spectra indicate oxygen incorporation at low deposition temperatures whether or not the native oxide was removed from the substrate prior to film deposition. Previously, transmission electron microscopy (TEM) has shown that all of the Ge films on GaAs (100) at room temperature and those deposited at 100 deg C on GaAs (100) having a native oxide are amorphous, while those deposited at 100 deg C on oxide free (100) GaAs are crystalline, but highly defective. Secondary ion mass spectroscopy (SIMS) measurements show that the films deposited at RT contain more than two orders of magnitude more oxygen than the films deposited at 100 deg C or a single crystal film deposited at 400 deg C. (16)O/(18)O diffusion studies definitively show that the excess oxygen in the films percolates in from the atmosphere. SIMS studies further reveal that thermally removing the GaAs substrate surface oxide or deposing a 1200A polycrystalline Au film on top of the Ge film has little effect on the incorporation of oxygen.