Basic ammonothermal GaN growth in molybdenum capsules

Abstract

Single crystal, bulk gallium nitride (GaN) crystals were grown using the basic ammonothermal method in a high purity growth environment created using a non-hermetically sealed molybdenum (Mo) capsule and compared to growths performed in a similarly designed silver (Ag) capsule and capsule-free René 41 autoclave. Secondary ion mass spectrometry (SIMS) analysis revealed transition metal free (< 1x10 17 cm -3 ) GaN crystals. Anomalously low oxygen concentrations ((2-6)x10 18 cm -3 ) were measured in a {0001} seeded crystal boule grown using a Mo capsule, despite higher source material oxygen concentrations ((1-5)x10 19 cm -3 ) suggesting that molybdenum (or molybdenum nitrides) may act to getter oxygen under certain conditions. Total system pressure profiles from growth runs in a Mo capsule system were comparable to those without a capsule, with pressures peaking within 2 days and slowly decaying due to hydrogen diffusional losses. Measured Mo capsule GaN growth rates were comparable to un-optimized growth rates in capsule-free systems and appreciably slower than in Ag-capsule systems. Crystal quality replicated that of the GaN seed crystals for all capsule conditions, with high quality growth occurring on the (0001) Ga-face. Optical absorption and impurity concentration characterization suggests reduced concentrations of hydrogenated gallium vacancies (V Ga -H x ). 4

Defects in Single Crystalline Ammonothermal Gallium Nitride

“…Reported impurities result from bulk GaN crystals grown in a) basic ammonothermal chemistries in a NiCr superalloy autoclaves without a liner (NiCr), within a silver capsule (Ag), within a molybdenum capsule (Mo) and b) acidic ammonothermal chemistries in a lined Ni-based alloy autoclave (lined) or a TZM autoclave (TZM). [22,26,32,43,58,59,79,[126][127][128] (7 of 18) 1600496…”

Ammonothermal Synthesis of Nitrides: Recent Developments and Future Perspectives

“…Meanwhile, growth rates beyond 300 mmday À1 in different crystallographic directionsw ere achieved. [11,12] Bulk GaNc rystals are of particular interestf or the fabrication of substrates, which enableh omoepitaxial growth of GaN layers foro ptoelectronic devices ("GaN-on-GaN").U sing this concept, semiconductor performances can be strongly increased due to the significantly lower defect concentrationsi ncomparison to the prevailing heteroepitaxialbased devices. [13,14] In recent years, the ammonothermal methodw as rediscovered as ap owerful tool for the synthesis of ternary and multinary nitrides and oxonitrides as well.…”

“…Researchers started to examine mineralizer systems, intermediates, solution equilibria, and solubilities to gain insight into crystallization processes within the crystal growth of GaN. Meanwhile, growth rates beyond 300 μm day −1 in different crystallographic directions were achieved . Bulk GaN crystals are of particular interest for the fabrication of substrates, which enable homoepitaxial growth of GaN layers for optoelectronic devices (“GaN‐on‐GaN”).…”

Ammonothermal Synthesis of Earth‐Abundant Nitride Semiconductors ZnSiN2 and ZnGeN2 and Dissolution Monitoring by In Situ X‐ray Imaging

“…Semiconductor performance can be extensively increased using single crystalline GaN wafers for homoepitaxial growth processes instead of conventional substrates like sapphire . Meanwhile, GaN growth rates over 300 μm per day in different crystallographic directions and single crystals with more than 50 mm in diameter have been demonstrated by the ammonothermal method . Ternary and quaternary nitrides can be synthesized ammonothermally as well, such as NaSi 2 N 3 , K 3 P 6 N 11 , and CaGaSiN 3 .…”