Study of epitaxial lateral overgrowth of semipolar (1 1 − 2 2) GaN by using different SiO2 pattern sizes

• We examine comparative studies of semipolar ELO-GaN film.
• Semipolar ELO-GaN film was grown by three step growth method.
• The achievement of smooth surface morphology of semipolar ELO-GaN.
• The crystal and optical properties was significantly improved by ELO process.

We investigated the growth mode and the crystal properties of lateral epitaxial overgrowth (LEO) semipolar (1 1 − 2 2) GaN by using the various SiO2 pattern sizes of 6, 8, 10 and 12 μm with the window width of 4.0 μm. By using three-step growth technique, we successfully obtained the fully-coalescenced semipolar (1 1 − 2 2) LEO-GaN films regardless of the SiO2 pattern sizes. However, the coalescence thickness of LEO-GaN film was decreased with decreasing SiO2 pattern size, indicating that the coalescence of semipolar (1 1 − 2 2) GaN was easily formed by decreasing the pattern size of SiO2 mask. The full width at half maximums (FWHMs) of X-ray rocking curves (XRCs) of LEO-GaN films decreased with increasing SiO2 pattern size. In the pattern size of 4 × 10 μm, we achieved the minimum XRCs FWHM of 537 and 368 arc s with two different X-ray incident beam directions of [1 1 − 2 − 3] and [1 − 1 0 0], respectively. Moreover, the photoluminescence bandedge emission of semipolar (1 1 − 2 2) GaN was 45 times increased by LEO process. Based on these results, we concluded that the LEO pattern size of 4 × 10 μm would effectively decrease crystal defects of semipolar (1 1 − 2 2) GaN epilayer, resulting in an improvement of the optical properties.

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