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|Type of Document
||Lift-Off of ZnSe-based Epilayer and Epitaxial growth of ZnSxSe1-x on it by LP-OMVPE|
|Date of Defense
ZnSe-based materials have excellent characteristics for blue light emitting devices. So the substrates used for the growth of ZnSe-based alloys are considered from three points of (1) lattice match, (2) thermal match, and (3) interdiffusion.
By replacing GaAs or GaP wafers by ZnSe substrates can avoid disadvantages of heteroepitaxy caused by lattice constant mismatch, by differential thermal expansion coefficients between substrate and epilayer. But the ZnSe substrate is cost too much. And it is not easy to achieve. So we choose the other way to get the substrate by Epitaxial Lift-Off (ELO). Another reason for this study is that the light extraction efficiency of these devices is limited by the optically absorbing GaAs substrate. So it can be improved by replacing GaAs with a new metal/glass substrate. The metallic interlayer can be used not only as an adhesive, but also as the reflective mirror to reflect light in the wafer-bonded LED structure.
In this study, ZnSe-epliayer have been successfully lifted-off from GaAs by etching solution (NaOH(1M): H2O2(30%) = 4:1 or NH4OH(30%): H2O2(30%) = 9:1) and adhered it onto Indium/glass. From PL spectra, the PL intensity and broad band increases after ELO. The broad band can be decreased by surface trimming of citric etching solution (C6H8O7: H2O: H2O2 = 30g: 30ml: 10ml). This etching process is helpful in regrown ZnSe-epilayer. Regrowth of ZnSSe with [H2Se]/[H2S]＝4 and II/IV=12.5, shows a NBE emission at 432nm with a FWHM of 26.6 meV at 77K PL spectrum. And the DAP is disappear after regrown. It means that the quality of ZnSe-epilayer becomes better after regrown.
||Chung-Cheng Chang - co-chair|
Wen-Tai Lin - co-chair
Wei-Chon Hun - co-chair
Ming-Kwei Lee - advisor
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|Date of Submission