Comparison of AlGaN and GaN grown on various substrates: Step flow growth on LiGaO2 at low growth temperature

AlGaN/GaN heterostructures were grown on LiGaO2 (LGO), sapphire, and hydride vapor phase epitaxy (HVPE) grown GaN substrates. Structural properties and surface morphology of each film was compared. LGO substrates produced the lowest FWHM values for both symmetric [Left Angle Bracket] 00.4 [Right Angle Bracket] and asymmetric [Left Angle Bracket] 10.5 [Right Angle Bracket] reflections. The films grown on LGO substrate also showed the best morphology. The small lattice mismatch of LGO to nitrides and Ga-polarity of grown films could be the primary reason for the smoother surface of AlGaN/GaN structure on LGO substrates. In developing the HFET structure on the LGO substrate, we have observed step flow growth in a structure with 300 angstroms thick Al0.25Ga0.75N on 2.4 µm thick GaN, which is very similar to the films grown by MOCVD. A high III/V flux ratio during growth and recently improved polishing of LGO substrates may have aided in promoting two dimensional step flow growth.

Duke Scholars

Author April S. Brown Electrical and Computer Engineering