High Quality Free-Standing GaN Substrate by Using Self-Separation Method

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 $8{\times}10^8cm^{-2}$ and $7{\times}10^7cm^{-2}$, 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.

Self-Separation 방법을 적용한 고품질 Free-Standing GaN