Molecular Beam Epitaxial (MBE) Growth of High Quality InP and Al0.48In0.52As

[摘要] This thesis concerns the growth and characterisation of InP grown by MBE and MOMBE; and AlInAs grown by MBE. The growth of undoped InP epitaxial layers using solid sources was examined. The quality of the layers was assessed using the techniques of capacitance voltage electrochemical (CV) profiling, photoluminescence (PL) and Hall effect measurement. By controlling systematically the three growth parameters of substrate temperature, growth rate and flux ratio, materials of improved quality were produced as shown by narrower PL line-width, and higher Hall mobilities. A thorough study of n-type doping in InP using sulphur generated from an electrochemical Knudsen source has been performed. The experimental results are explained in terms of a kinetic model of sulphur incorporation and desorption in conjunction with a thermodynamic analysis of the effect of substrate temperature and flux ratios. The results show that sulphur is a controllable dopant with well defined behaviour in InP. An attempt has been made to produce p-type InP using magnesium doping. The electrical and optical properties of these doped layers were comparable to the undoped samples. However, the surface morphology of the doped samples was found to deteriorate as the magnesium flux was increased. However there was little effect on the electrical or optical characteristics. Epitaxial InP layers grown by MOMBE at BTRL were also characterised. Magnesium, sulphur and silicon were found to be the residual shallow impurities present in these samples. Deep Level Transient Spectroscopy (DLTS) measurements shows that all electron traps observed in the MOMBE material have already been observed in InP grown by solid sources. Impurity band conduction exists in these samples which dominates the Hall measurements at low temperatures. The MOMBE samples have comparable electrical and optical properties to the best InP layers grown by solid source MBE. The ternary compound of AlInAs grown lattice matched to InP was characterised. During growth it was observed that there is a region of substrate temperature which produces a rough surface. This region of rough surface growth was correlated with an increase in the PL line-width as well as the appearance of unique deep traps in the DLTS measurements. Growth at elevated temperatures led to an increase in the loss of indium leading to mismatched layers. The thesis concludes with a study of PL recombination mechanisms associated with the observed emission spectrum from AlInAs. Using a Diamond Anvil Cell (DAC) the PL dependence on hydrostatic pressure was determined.

[发布机构] University:University of Glasgow

[关键词] Materials science, Condensed matter physics