| Summary: | 博士 === 國立交通大學 === 材料科學與工程學系 === 101 === Future CMOS technology will aim at the integration of InGaAs semiconductor on silicon substrates for low-cost, light-weight, large area and high-performance logic devices. The first step toward the goal of InGaAs/Si is to obtain high-quality thin GaAs (or Ge) on Si substrate, then, InGaAs compound will be grown on the alternative GaAs (Ge)/Si substrates. Therefore, this dissertation concentrates on the growth of high-quality In0.5Ga0.5As epitaxial films on GaAs substrate for MOSCAP device application by using MOCVD growth method.
For the purpose of study, the effects of growth conditions and subtract misorientation degrees of GaAs substrate on crystal quality and surface morphology of In0.3Ga0.7As epilayers were first investigated. The epilayers were grown using step graded buffer layers on different misoriented GaAs (001) substrates. AFM images show that smooth-surface In0.3Ga0.7As film with a RMS roughness of 1.5 nm was obtained at the growth temperature of 490 oC. The threading dislocation (TD) density of about 1x106 cm-2 in the film was determined by TEM. The photoluminescence results obtained at 300 and 77 K indicate that very low recombination centers existed in the epilayer.
High-quality smooth surface In0.5Ga0.5As epilayers have been successfully grown on the GaAs substrate. A cross-section study by TEM showed that the TDs have been successfully contained and limited within the buffer layers designed to stop the elongation of TDs into In0.5Ga0.5As epilayers. In our work, a TD density of 1x106 cm-2 in a fully relaxed In0.5Ga0.5As epilayer was achieved. The measurement for lifetimes of n- and p-type In0.5Ga0.5As was performed by using time-resolved photoluminescence, confirmed a great reduction on the recombination centers in the In0.5Ga0.5As epilayers.
High-quality In0.5Ga0.5As epilayers allow us to fabricate high-performance In0.5Ga0.5As-based metal-oxide-semiconductor capacitor (MOSCAP) on GaAs substrate. The performance of the MOSCAPs is comparable to that of In0.53Ga0.47As/InP based devices grown by molecular beam epitaxy technique. The devices show a nice capacitance-voltage response, with small frequency dispersion. The parallel conductance contours show the free movement of Fermi level with the gate bias. Acceptable interface trap density Dit value of 5E11-2E12 eV-1cm-2 in the energy range of 0.64-0.52 eV above the InGaAs valence band maximum in In0.5Ga0.5As/GaAs MOSCAPs obtained by conductance methods was shown.
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