Research On Free-Standing GaN Substrate

Based on great progress of GaN growth on the silicon substrate,a kind of method of Free-standing GaN substrate is proposed in this paper.First,using an AlN buffer layer and AlN intertlayer technology,2μm crack-free GaN thin films on silicon substrate were grown by MOCVD.Second,the stress of the GaN film was released by chemical etching to remove the silicon substrate.Finally,thicker GaN thin film whose thickness ranges from 20μm to 100μm was grown on such templates by HVPE and forming free-standing GaN substrates.We designed and processed a fixture which strips GaN,and has successfully stripped 2μm thick GaN thin film of 10×10mm.The measurement of GaN layer before and after be stripped is made by XRD.The result is that the FWHM of the rocking-curve of lift-off GaN(0002) surface slightly decrease.The C-axis lattice parameter of lift-off GaN thin film is close to the standard crystal constant.The result showed the stress after being stripped is calculated and it released to sme extent.The film is in completely relaxed state.Free-standing GaN substrate is grown on GaN-bonding on quartz template by HVPE.