Growth temperature dependence of structural properties for single crystalline GaN films on MgAl_2O_4 substrates by pulsed laser deposition

摘要

Epitaxial growth of GaN films on MgAl_2O_4(111) substrates by pulsed laser deposition (PLD) at temperatures ranging from 973 K to room temperature (RT) has been carried out in this work. It is found that the thickness of the interfacial layer between GaN and MgAl_2O_4 decreases with a decrease of growth temperature and the interfacial reaction is completely suppressed in the case of RT growth. The epitaxial relationship between GaN and MgAl_2O_4 is GaN(0001)∥MgAl_2O_4(111) and GaN [1120]∥ MgAl_2O_4[011] at all temperatures. The crystal quality of the as-grown GaN changes with the growth temperature and the RT-grown GaN shows the best quality with FWHM values of 0.21° for the tilt distribution and 0.37° for the twist distribution, respectively. Only the growth of GaN at RT can completely suppress the diffusion of Mg from the substrate to the GaN film. These results evidently demonstrate the advantages of RT growth of GaN on MgAl_2O_4 substrates by PLD.