Progress in Near-Equilibrium Ammonothermal (NEAT) Growth of GaN Substrates for GaN-on-GaN Semiconductor Devices

This paper reviews the near-equilibrium ammonothermal (NEAT) growth of bulk gallium nitride (GaN) crystals and reports the evaluation of 2 '' GaN substrates and 100 mmbulk GaN crystal grown in our pilot production reactor. Recent progress in oxygen reduction enabled growing NEAT GaN substrates with lower residual oxygen, coloration, and optical absorption. The oxygen concentration was approximately 2 x 10(18) cm(-2), and the optical absorption coefficient was 1.3 cm(-1) at 450 nm. Maps of full-width half maximum (FWHM) of X-ray diffraction rocking curveswere generated for grown crystals and finished wafers. The X-ray rocking curve maps confirmed high-quality and uniform microstructure across the entire surface of the bulk crystals and substrates. The average FWHM of the 50 best bulk crystals from the recent batch was 28 +/- 4 arcsec for the 002 diffraction and 34 +/- 5 arcsec for the 201 diffraction, with an average radius of curvature of 20 m. X-ray topography measured on both sides of the bulk crystals implied that the density of dislocations wasreduced by one order of magnitude during the NEAT growth. A typical NEAT GaN substrate shows dislocation density of about 2 x 10(5) cm(-2).

Automated summary

This paper reviews the near-equilibrium ammonothermal (NEAT) growth of bulk gallium nitride (GaN) crystals, and evaluates the quality of 2 '' GaN substrates and 100 mm bulk GaN crystal grown in a pilot production reactor. Oxygen reduction advancements have led to lower residual oxygen, coloration, and optical absorption in NEAT GaN substrates. X-ray diffraction rocking curve maps confirmed high-quality and uniform microstructure across the entire surface of the crystals and substrates, with a significant reduction in dislocation density during NEAT growth.