popovici-mrssp-468-3

Data for reference popovici-mrssp-468-3

Impurity Contamination of GaN Epitaxial Films From the Sapphire, SiC, and ZnO Substrates

Galina Popovici, Wook Kim, Andrei Botchkarev, Haipeng Tang, James Solomon, Hadis Morkoç

Materials Research Society Symposium Proceedings 468, 3 (1997).

Below is the abstract submitted to the meeting, not the abstract of the published paper:
The lack of an ideal substrate presents a major problem in GaN growth. Good quality GaN layers have been grown heteroepitaxially on sapphire (Al₂O₃), 6H-SiC, ZnO in an effort to optimaze layer performance. Using substrates other than native GaN substrate presents not only formidable challenges in terms of: the lattice and thermal mismatch, but also a contamination from substrates during growth. While the influence of the thermal and lattice mismatches of non native substrates on the GaN crystal structure and defect content have been studied extensively, there are no, for our knowledge, reports on the possible contamination of the GaN layers from the substrates during growth. In the current investigation, the contamination of GaN films by impurities from the Al₂O₃, SiC and ZnO substrates during growth has been studied by secondary ion mass spectrometry. analysis. The amount of all measured impurities is larger near the interface with the substrate within the distance of 0.3-0.4 mm. This near the substrate region has many dislocations and stacking faults as determined by TEM. This highly defective region allows impurities to incorporate more readily in the as compared to the equilibrium solubility in a perfect crystal at a given temperature. SIMS measurements in GaN layers grown on SiC and sapphire showed large amounts of Si and O, respectively, within a region wider than the highly disordered near the interface pointing to the possibility of the impurity diffusion from the substrate during growth. The qualitative trend observed is quite clear and significant. This result points once more to the necessity of the developing native GaN substrates.

This paper is part of Gallium Nitride and Related Materials II

Contributed by Materials Research Society

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