Growth of bulk AlN single crystals with low oxygen content taking into account thermal and kinetic effects of oxygen-related gaseous species

Kinetic models in the system Al–N–O–C–H are useful to predict the time- and temperature-dependent influences of oxygen related species on aluminum nitride (AlN) bulk crystal growth by the sublimation–recondensation (also known as physical vapor transport, PVT) method. The transient oxygen incorporation is modeled based on non-linear regression analyses of experimental mass spectrometric data performed at conditions comparable to those of PVT crystal growth, and can be calculated for any user-specified temperature program. The results are in good qualitative agreement with SIMS measurements taken at several positions along the growth direction of a seeded isometric aluminum nitride crystal. By optimizing growth set-up geometry, source purification process, and growth parameters, the impurity content for the grown crystals decreases significantly to values of 6 ppm, 15 ppm, and 30 ppm for O, Si, and C, respectively, 2.5 mm above the AlN seed–crystal interface.

► Continuous increase in single crystal size by forced seed enlargement.
► Predicting the time- and temperature-dependent influence of oxygen.
► Impurity content decreases significantly during initial growth.