New fabrication method of InGaN laser diode by epitaxial lateral overgrowth and cleavable technique from free-standing non- and semi-polar GaN substrate

We propose a new Fabry-Perot (FP) GaN laser fabrication method utilizing an epitaxial lateral overgrowth (ELO) technique and m-plane cleavability of the GaN crystal. The removed m-plane InGaN laser having a lasing wavelength 408. 1 nm operated at a low threshold current density as low as 2.15 kA/cm². First, unlike a conventional ELO growth technique, we avoid coalescence between adjacent ELO layers, thus forming island-like ELO layer bars, which were later used as the base for FP GaN laser. Then, a laser device epilayers were epitaxially grown and laser ridge structure was fabricated on each of these non-coalesced island-like ELO base layers. Island-like ELO laser bar formation facilitates an easy removal of the laser bars mechanically using a commercially available adhesive polymer film. Our investigation found that cleavable m-plane of the GaN crystal assists in the liftoff of the fabricated m-plane InGaN FP lasers. We further confirm that the reported fabrication method can be adopted to semi-polar crystal plane orientations of GaN.