On the laser detachment of n-GaN films from substrates, based on the strong absorption of IR light by free charge carriers in n +-GaN substrates

Abstract

The physical and technological basics of the method used to lift off lightly and moderately doped n-GaN films from heavily doped n + -GaN substrates are considered. The detachment method is based on the free-charge-carrier absorption of IR laser light, which is substantially higher in n + -GaN films.

Laser slicing: A thin film lift-off method for GaN-on-GaN technology

“…The ion implantation method does not allow separating epitaxial device structures due to a large number of point defects formed by the implantation process [38,39,41]. The freecarrier-absorption LLO method is limited to separating undoped films from a heavily doped substrate [40].…”

“…To separate a GaN film from a native GaN substrate several approaches were proposed: chemical lift-off process [30]; porous release layers created by chemical [31], electrochemical [32,33] or dry [34] etching of GaN substrate; controlled spalling [35]; laser lift-off with an In-GaN release layer [5]; ion implantation [36][37][38][39]; and freecarrier-absorption laser lift-off [40].…”