Growth and electron microscopy study of GaN/MgAl₂O₄ heterostructures

Abstract

We successfully grew Gallium nitride (GaN) films on MgAl 2 O 4 (111) substrates using low temperature pulsed laser deposition (PLD). X-ray diffraction rocking curves revealed the high quality of as-grown GaN with its full width at half maximum (FWHM) along [0002] as small as 0.088. Atomic force microscopy images showed very smooth surface of as-grown GaN and indicated a two-dimensional growth. High-resolution transmission electron microscopy showed high structural perfection of GaN films. The crystalline structure for MgAl 2 O 4 substrate from its body to its top part adjacent to GaN epitaxy kept constant, and the interface between GaN and MgAl 2 O 4 was atomically abrupt. We attribute the high quality of as-grown GaN films to the well-controlled Mg atom evaporation from MgAl 2 O 4 substrate surface owing to the application of low growth temperature in PLD: on the one hand, it avoids the severe interfacial reaction that is very likely to take place in conventional MOCVD or MBE growth, and hence makes the epitaxial growth possible; on the other hand, it conserves the crystalline structure of the substrate surface, and consequently takes good advantage of the small lattice mismatch between GaN and MgAl 2 O 4 .

Microstructure and interface control of GaN/MgAl2O4 grown by metalorganic chemical vapor deposition: Substrate-orientation dependence

“…17,[20][21][22][23] Except for our previous report, 24 few studies have systematically described that the surface evolution is caused by thermal passivation of MgAl 2 O 4 substrates. In addition, the substrate-orientation dependence of the microstructure and interface chemistry of the GaN/MgAl 2 O 4 interface have not yet been investigated.…”

Epitaxial growth of GaN films on unconventional oxide substrates

“…Li et al achieved the high-quality GaN lms on MgAl 2 O 4 (111) substrates at low temperature by PLD. 49,50 XRC shows that the FWHM of GaN ( 0002) is only 0.07 , indicating the high crystalline quality of the GaN epitaxial layer. Fig.…”

Epitaxial growth of group III-nitride films by pulsed laser deposition and their use in the development of LED devices

“…There is no doubt that interfacial reaction should be eliminated in order to grow high-quality group IIInitride films on MgAl 2 O 4 substrates. One approach is to grow III-nitride films on MgAl 2 O 4 substrates by PLD at low temperature [45,[88][89][90].…”

“…For instance, LiGaO 2 (100) substrate is beneficial for the nucleation of m-plane GaN (4.0% lattice mismatch against c LiGaO 2 , and 0.1% lattice mismatch against b LiGaO 2 ). The last but not least, the group III-nitrides usually can be easily peeled off from the unconventional oxide substrates by chemicals due to the fact that the unconventional oxide substrates easily react with acids or alkalis [10], which makes free-standing nitride substrates or vertical structural devices possible [45]. Undoubtedly, the unconventional oxide substrates will play a critical role in the fabrication of group III-nitride films and their relevant devices.…”