The epitaxial lateral overgrowth (ELO) of GaN with a stripe tungsten (W) mask pattern is performed by hydride vapor phase epitaxy (HVPE) and a buried structure of the W mask with a smooth surface is achieved for the stripe mask patterns of <1120> and <1100> direction. Optical and crystalline characteristics of the ELO-GaN are investigated by means of cathodoluminescence (CL) imaging and X-ray rocking curves (XRCs). It is found that the CL intensity at 133 K due to the near-band edge emission is stronger in the laterally overgrown region in comparison with that in the normal growth region. The φ-ω scan of XRCs reveals that the tilting of the c-axis is much smaller in the ELO-GaN grown with the W mask than that grown with an SiO2 mask.

We studied selective area growth (SAG) of GaN using a tungsten (W) mask with an atmospheric metalorganic vapor phase epitaxy (MOVPE) system. No GaN polycrystals were observed on the W mask regions, and the selectivity of GaN growth on window regions proved to be excellent. The GaN stripes developed into different shapes depending on the direction of stripe mask patterns. If the stripe was along <1120>, a triangular shape with {1101} facets was formed. If the stripe was along <1100>, a trapezoidal shape with a smooth (0001) surface on top and rough surfaces on both sides was obtained. The lateral overgrowth of GaN on the W mask occurred in both cases. The growth mechanisms and the facet formation were similar to those found in SAG using a SiO2 mask.

Selective area growth (SAG) and epitaxial lateral overgrowth (ELO) of GaN using tungsten (W) mask by metalorganic vapor phase epitaxy (MOVPE) and hydride vapor phase epitaxy (HVPE) have been studied. The selectivity of the GaN growth on the W mask as well as the SiO 2 mask is excellent for both MOVPE and HVPE. The ELO-GaN layers are successfully obtained by HVPE on the stripe patterns along the < > 1 1 00 crystal axis with the W mask as well as the SiO 2 mask. There are no voids between the SiO 2 mask and the overgrown GaN layer, while there are triangular voids between the W mask and the overgrown layer. The surface of the ELO-GaN layer is quite uniform for both mask materials. In the case of MOVPE, the structures of ELO layers on the W mask are the same as those on the SiO 2 mask for the < > 1120 and < > 1 1 00 stripe patterns. No voids are observed between the W or SiO 2 mask and the overgrown GaN layer by using MOVPE.

A buried tungsten (W) mask structure with GaN is successfully obtained by epitaxial lateral overgrowth (ELO) technique via low-pressure metalorganic vapor phase epitaxy (LP-MOVPE). The selectivity of GaN growth on the window region vs. the mask region is good. An underlying GaN with a striped W metal mask is easily decomposed above 500 °C by the W catalytic effect, by which radical hydrogen is reacted with GaN. It is difficult to bury the W mask because severe damage occurs in the GaN epilayer under the mask. It is found that an underlying AlGaN/GaN layer with a narrow W stripe mask width (mask/window = 2/2 νm) leads the ELO GaN layer to be free from damage, resulting in an excellent W-buried structure.

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