[19p-PA4-1~27] 15.4 III-V-group nitride crystals

[19p-PA4-19] Reuse process of sapphire substrates for GaN epitaxial growth using laser lift-off technique

〇Issei Watanabe¹, Shin Tabata², Kunimitsu Takahashi², Akifumi Kasamatsu¹ (1.NICT, 2.DISCO)

Keywords:Laser lift-off, GaN-HEMT epitaxial structure, Reuse and recycle of sapphire substrate

We have fabricated GaN-based high electron mobility transistors (HEMTs) on sapphire, SiC, Si and GaN substrates, and have reported f_T and f_max over 200 GHz. To apply GaN-HEMTs to millimeter- and terahertz-wave MMICs, it is necessary to thin the substrate for GaN epitaxial growth to about 100 µm. However, sapphire and SiC substrates need to be thinned by dry etching or mechanical polishing since they are resistant to acid and/or alkali solutions, which means most of the substrate material is discarded. In this study, we removed GaN-HEMT epitaxial structure from a sapphire substrate using a short-pulse laser and re-grew the same structure on the recycled sapphire substrate. We found that their characteristics are almost the same. These results indicate that we can reuse and recycle sapphire substrates for GaN epitaxial growth using laser lift-off technique.