Kazuyuki IIzuka

Realization of Low Dislocation GaN/Sapphire Wafers by 3-Step Metalorganic Vapor Phase Epitaxial Growth with Island Induced Dislocation Control

A novel dislocation reducing mechanism was successfully introduced into the conventional 2-step metalorganic vapor phase epitaxial (MOVPE) growth method of GaN/sapphire wafer by inserting an additional intermediate-temperature (IT)-GaN buffer between the low-temperature (LT)-GaN buffer and the main high-temperature (HT)-GaN layer. During the growth of the IT-GaN buffer, high-density islands with faceted slopes were formed. Vertically propagating dislocations from the GaN/sapphire interface were bent at the faceted slopes so as to gather at the island/island boundaries, where dislocation loops were formed efficiently. Due to such an island induced dislocation control mechanism, the dislocation density was reduced markedly from the 109 cm-2 range to the mid-108 cm-2 range during the growth of the IT-GaN buffer. As a result, the GaN/sapphire wafers with low dislocation density of 3×108 cm-2 were successfully grown by such a 3-step MOVPE method, whereas high-density dislocations (1×109 cm-2) remained in the final GaN/sapphire wafers grown by the conventional 2-step growth method without dislocation control.

Structural evaluation of defects in β-Ga2O3 single crystals grown by edge-defined film-fed growth process

We have structurally evaluated β-Ga2O3 crystals grown by edge-defined film-fed growth process using etch pitting, focused ion beam scanning ion microscopy, transmission electron microscopy, and related techniques. We found three types of defects: arrays of edge dislocations corresponding to etch pit arrays on -oriented wafers, platelike nanopipes corresponding to etch pits revealed on the (010)-oriented wafers, and twins including twin lamellae.