Controlling a three dimensional electron slab of graded AlxGa1−xN

Abstract

Polarization induced degenerate n-type doping with electron concentrations up to ∼10 20 cm −3 is achieved in graded Al x Ga 1−x N layers (x: 0%→37%) grown on unintentionally doped and on n-doped GaN:Si buffer/reservoir layers by metal organic vapor phase epitaxy. High resolution x-ray diffraction, transmission electron microscopy and electron energy loss spectroscopy confirm the gradient in the composition of the Al x Ga 1−x N layers, while magnetotransport studies reveal the formation of a three dimensional electron slab, whose conductivity can be adjusted through the GaN(:Si) buffer/reservoir. * rajdeep.adhikari@jku.at † alberta.

Polarization Effects in Graded AlGaN Nanolayers Revealed by Current-Sensing and Kelvin Probe Microscopy

“…The observed field distribution in a real structure can be explained by a complex superposition of induced electric fields in the bulk structure, peculiarities of their manifestation on the surface of the cross-section, and the impact of extended structural defects, particularly penetrating dislocations. As noted above, the template–buffer interface is not electrically neutral, which is a typical phenomenon; ,, thus, the buffer layer cannot be considered as neutral. On the other hand, the top GaN layer coating structure is in contact with the dielectric glue and the neighboring sample.…”

“…Thus, nanowires contain a very different population of surface states from epitaxial thin films. Moreover, the graded Al x Ga 1– x N nanowires were grown on p-type Si (111) substrates, and as has been recently shown, , the Hall concentration of a 3DEG in graded Al x Ga 1– x N layer depends on the electron concentration in the buffer/substrate/reservoir. Thus, the magnitude of %Al/nm for deep donor compensation in the case of graded Al x Ga 1– x N layers still remains unclear.…”

(Invited) Polarization-Induced Doping in Graded AlGaN Epilayers Grown on AlN Single Crystal Substrates

“…The free carriers are n-type (electrons) in increasing composition epilayers, or p-type (holes) in decreasing composition epilayers. Both n-and p-type doping have been demonstrated in graded, Garich AlGaN epilayers grown by molecular beam epitaxy (MBE) and metal-organic chemical vapor deposition (MOCVD) (12,13,(17)(18)(19). A limited number of studies have been performed on Al-rich alloys grown on c-plane sapphire substrates (20)(21)(22), where the dislocation density is high, but reports of growth on low defect density substrates are lacking.…”

Cross-plane thermal conductivity of GaN/AlN superlattices

“…The tuneable bandgap, high thermal stability, high electric field strength, high electron mobility, and the presence of a spontaneous and piezoelectric polarization in wurtzite IIInitrides led to the integration of GaN and its alloys in stateof-the-art electronics technology 1 . Current III-nitride based devices range from light emitting diodes in the ultraviolet 2,3 and visible range 4,5 to high-electron mobility transistors [6][7][8] and biosensors 9 . Another research field involving III-nitrides is opened up by doping them with transition metals and by studying the emergent spin related phenomena [10][11][12][13] .…”