Materials Research Society Symposium Proceedings 468, 167 (1997).
Below is the abstract submitted to the meeting, not the abstract of the published paper:
The performance of GaN films for light emitting diodes (LEDs) devices with high emission efficiencies is surprisingly determined by the high concentration of extended dislocations which are mainly caused by the large lattice mismatch (>12 %). The lack of suitable substrate which is both lattice and thermally matched with the GaN is a serious obstacle to improving the crystalline quality of the GaN. We present here our study on use of new substrate, LiGaO2, which is better lattice and thermally matched to the GaN. Microstructures of GaN films gown on the LiGaO2 by metalorganic chemical vapor deposition (MOCVD) have been characterized by transmission electron microscopy (TEM) and high resolution transmission electron microscopy (HRTEM). TEM and HRTEM results show that high quality single-crystal wurtzite GaN films have been deposited on the LiGaO2. A high density of threading dislocations and stacking faults have been observed in the GaN films. Threading dislocations with burgers vector b = a/3 are the predominant type formed in the GaN films. Also, the GaN films contain some inversion domain boundaries. Both TEM and HRTEM results reveal that there is an unexpected amorphous or nanocrystalline interlayer between the GaN and the LiGaO2 with a thickness of 50-100 nm, even though the lattice mismatch of GaN to LiGaO2 is only 1%. The formed interlayer may be due to nitridation of the LiGaO2 during the growth of the GaN film. Further results on the characterization of the nature and origin of this interlayer and its effects on the subsequent microstructure will be presented.
This paper is part of Gallium Nitride and Related Materials II
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