Homoepitaxial growth of high structural quality and high-purity thick gallium nitride layers by crystallization from vapor phase (hydride vapor phase epitaxy (HVPE)) on 1, 1.5, and 2 inch substrates obtained by a solution (ammonothermal) growth method is presented. Advantages and disadvantages of both growth technologies are described in detail. Structural, optical, electrical, and thermal properties of gallium nitride grown from the vapor phase are demonstrated and compared to properties of ammonothermally grown material. It is shown that a synergy of these two methods can create new opportunities for an efficient production of bulk gallium nitride crystals and then substrates. It is also shown that free-standing (products of slicing procedures) gallium nitride crystals obtained from growth by vapor phase on ammonothermal substrates can be successfully used as seeds for the next growth process by both discussed methods. Factors limiting HVPE and making it a 'wafer to wafer' technology are presented, clarified, and analyzed. Intentional introduction of silicon to growth of gallium nitride by HVPE and crystals with a high free carrier concentration and high structural quality are demonstrated. First electronic and optoelectronic devices fabricated on the free-standing gallium nitride substrates are shown.

Crystallization of GaN by hydride vapor phase epitaxy (HVPE) on ammonothermally grown GaN seed crystals is described. The initial growth conditions for HVPE are determined and applied for further bulk growth. Smooth GaN layers up to 1.1 mm thick and of excellent crystalline quality, without cracks, and with low dislocation density are obtained. Preparation of the free-standing HVPE-GaN crystal by slicing and structural and optical quality of the resulting wafer are presented.

It is demonstrated in this paper that 1.9-mm-thick gallium nitride grown by Hydride Vapor Phase Epitaxy (HVPE) on an ammonothermally grown GaN seed can reproduce the structural, in terms of defects, properties of the seed. The etch pit density and its correlation to the threading dislocation density in the ammonothermal GaN substrate and the HVPEGaN layer is presented and analyzed. However, it has recently been observed that for HVPE-GaN thicker than 2 mm some additional defects are formed in the new grown material. Therefore, three HVPE growth runs were performed in the same experimental conditions, using three structurally identical ammonothermally grown GaN seeds of different thicknesses. The influence of the thickness of the seeds on the crystallization process and the properties of the HVPE-GaN layers is shown and discussed.