In this paper, we discuss β-Ga₂O₃ thin films that have been grown on freestanding GaN (FS-GaN) using furnace oxidation. A GaN template was grown by horizontalhydride vapor phase epitaxy (HVPE), and FS-GaN was fabricated using the laser lift off (LLO) system. To obtain β-Ga₂O₃ thin film, FS-GaN was oxidized at 900~1,100℃. Surface and cross-section of prepared β-Ga₂O₃ thin films were observed by field emission scanning electron microscopy (FE-SEM). The single crystal FS-GaNs were changed to poly-crystal β-Ga₂O₃. The oxidized β-Ga₂O₃ thin film at 1,100℃ was peel off from FS-GaN. Next, oxidation of FS-GaNwas investigated for 0.5~12 hours with variation of the oxidation time. The thicknesses of β-Ga₂O₃ thin films were measured from 100 nm to 1,200 nm. Moreover, the 2-theta XRD result indicated that (-201), (-402), and (-603) peaks were confirmed. The intensity of peaks was increased with increased oxidation time. The β-Ga₂O₃ thin film was generated to oxidize FS-GaN.

We demonstrated that self-separation FS-GaN (freestanding-GaN) was grown on MELO (maskless epitaxially lateral overgrowth) GaN template by horizontal HVPE (hydride vapor phase epitaxy). Before thick GaN grwoth, MELO GaN template was grown on patterned GaN template by MOCVD (metal organic chemical vapor deposition). The laterally overgrown GaN would consist of a continuous well coalesced layer. The mixed TDD (threading dislocation density) of seed and wing region were 8 × 10⁸ cm-2 and 7 × 10⁷ cm^-2, respectively. After thick GaN grown by HVPE, the self-separation between thick GaN and sapphire substrate was generated at seed region. The regions of self-separation for FS-GaN and sapphire were observed by FE-SEM. Moreover, Raman results indicated that the compressive strain of seed and wing regions at FS-GaN substrate were slightly released compared to that of thick GaN grown on conventional GaN template. The optical properties of the FS-GaN substrate were examined by using PL (photoluminescence). The PL exhibited that donor bound exciton and donor acceptor pair were observed at low temperature. The effects on optical and structural properties of FS-GaN substrate have been discussed in detail.