Investigation Of The Transfer Of GaN LED Films From Silicon Substrate To Electroplating Metal Substrate

Plating metal substrate has the most prominent advantages of enhancing the thermal conductivity, optical and electrical properties of GaN LED, especially the high-power GaN LED. At present, there has been an extensive investigation on the GaN films transfer from sapphire or SiC substrate to plating substrate. Whereas, there has been a few reports about the transfer of silicon substrate GaN films, and by now even no research on the stress transformation in the film transfer, according to our knowledge。In this thesis, plating and chemical etching method was adopted to transfer GaN films from silicon to metal substrate, and the stress transformation caused by transfer was researched by HRXRD (high resolution X-ray diffraction) and PL (photoluminescence)method. In addition, for the improvement of substrate structure, pattern plating method was investigated. To sum up, the main content of this thesis and some main conclusions are as follows:1. Three kinds of plating substrates were prepared, including copper, chrome and copper/nickel/copper substrates. Then HRXRD and PL were used to investigate the stress of GaN films on those plating substrates. And the stress analysis showed that, the tensile stress in GaN films caused by epitaxial growth can be released when GaN films was transferred to those plating substrates from silicon substrate. And the GaN films on chrome substrate had a least tensile stress.2. In this thesis, the chrome substrate were composed of copper transition layer and chrome sustentation layer. Then the thickness of chrome sustentation layer was investigated. And it was recognized that the thickness of chrome sustentation layer had no obvious influence on the stress of GaN films on the chrome substrate.3. In this thesis, photoresist was used to cover the groove on the wafer, which can made metal meterial electrodeposite dividually in the plating process. And the copper substrate fabricated by this method showed a transparent pattern with thickness of about 20 micron. Afterward, the thickness of pattern copper substrate reached about 40 micron by using that method twice, however, the second copper layer presented a rough edge.4. In this thesis, it was recognized that chrome can not electrodeposite directly on platinum. So platinum was deposited on the groove, in order to prevent chrome form above the groove. However, the chrome substrate prepared by this method can not show any pattern, because some platinum fell off the groove before plating and the rest platinum can be coverd by chrome which growed from side, not directly electrodeposited on platinum.