| Summary: | 碩士 === 中原大學 === 電子工程學系 === 85 ===
Among all semiconductors, the most important ones for visible LEDs are the ternary and the quaternary alloy systems. To be free of mismatch problem during epitaxial growth of the above material systems, new methods that can be employed to develop desired lattice of alloy substrate are required. When GaAs is mixed with GaP, a ternary alloy is formed having an energy gap between those of GaAs and GaP Using this GaAs to GaAsP layer converting technique, GaAsP alloy layers with the composition range changing from 0.25 to 0.75 can be easily obtained on GaP substrates.
This composition converting technique is composed of two steps. First, a GaAs layer is grown on a GaP(111)B substrate. Second, the GaAs layer converts its composition to GaAsP alloy when contacts with the saturated Ga-As-P solution. The thickness of the grown layers is measured by observing the cleaved and stained cross-section of samples by Nomarski and atomic force microscopes. The composition of the grown layer was determined by x-ray diffraction. According to the x-ray measurement results, the composition ratio x of the GaAs1-xPx layer is not constant under the same contents of solute and solvent. The range of composition variation is between 0.3 to 0.67. From the PL spectra, the peak intensity of GaAs1-xPx converted layer is even stronger than that of VPE GaAsP layer .The good optical evaluation results of this study present the possibility to fabricate optical devices on the converted GaAsP epitaxial substrate.
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