MBE growth and HRXRD characterization of III-nitrides (AlN and InxAl1-xN)



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Development of III-nitride (III-N) materials such as aluminum nitride (AlN) and indium aluminum nitride alloys (InxAl1-xN) on silicon (Si) is of great interest due to numerous advantages of this substrate. These advantages include low cost, availability in large size, good thermal and electrical conductivities, high mechanical strength, and the potential for integration with Si-based devices.

AlN is a wide band gap (6.2 eV) semiconductor with applications in deep-ultraviolet photo detectors and in the fabrication of high efficiency field emitters, due to nearly zero electron affinity. AlN is also used as a buffer layer for GaN-based device structures heteroepitaxially grown on foreign substrates. Despite recent progress, the initial stage of AlN growth on Si is not clearly understood, and the debate related to the optimal nucleation conditions for AlN buffer layer still continues. In addition, most research in III-N is focused on materials and heterostructures grown in the III-polar direction on Si (111); however, the N-polar orientation has several advantages that make it attractive for development of LEDs and high electron mobility transistors (HEMTs).

InxAl1-xN alloys with low indium content have potential applications in HEMT devices. Alloys with high InN composition (~18%) have a lattice matched structure with GaN; a higher refractive index of InxAl1-xN along with a close lattice match to GaN makes it attractive as a cladding layer in optical devices. In spite of recent progress, researchers have faced difficulty in growth of alloys with InN composition ‘x’ > 2%. This difficulty is due to the low growth temperatures required for Indium incorporation and the resulting low ammonia decomposition. We have demonstrated InxAl1-xN alloys with InN composition between 2% and 10%, on Si substrates, by changing the growth temperature.



III-Nitrides, GSMBE, PAMBE, XRD, XRR, Silicon, Plasma, AlN, InAlN, Characterization, Growth