Growth and characterisation of dilute nitride antimonide layers by plasma-assisted molecular beam epitaxy

摘要

The work presented in this thesis is concerned with the growth and characterisation of III-NSb films by plasma-assisted molecular beam epitaxy (PA-MBE). The research was motivated by their application in technologically important regions of the IR spectrum. Homoepitaxial growth of GaSb films was conducted and characterised as a function of V:III ratio and growth temperature, permitting observation of morphology changes with growth conditions, also providing insight into surfaces of the ternary dilute nitride. Heteroepitaxial GaSb/GaAs growth has highlighted defect formation and propagation arising from lattice mismatched deposition. Films of GaNxSb1-x, a material of interest for device applications in the 2-5 μm spectral range, have been grown on GaSb(001) substrates. The results demonstrate the degree to which substitutional N content may be controlled through variation of the temperature and rate of deposition. Models based upon kinetic and thermodynamic principles and previously applied to GaNxAs1-x have been evaluated for N content of GaNxSb1-x films as a function of the rate and temperature used for growth. The growth of InNxSb1-x, an alloy of significance in the technologically important wavelength region of 8-12 μm, upon InSb(001) substrates is described. There is qualitative agreement with the temperature dependence of N content. Analysis of the substitutional N content as a function of growth rate, however, suggests a difference between GaNxSb1-x and GaNxAs1-x. An explanation is presented for the trend in the level of substitutional N uptake across III-V-N materials. Further experiments are proposed to extend the parameter space sampled in the investigation of GaNxSb1-x and InNxSb1-x films, with regard to the Sb:III ratio employed during growth. Initial results are reported from measurements undertaken with a pyrometer operating at 1.6 μm, suggesting that growth can be conducted at lower temperatures. Additional preliminary results are presented for the growth of GaxIn1-xNySb1-y films, demonstrating a tuneable band gap quaternary material, lattice matched to GaSb is possible.