Epitaxial overgrowth of GaN nanocolumns

Abstract

Reactive molecular-beam epitaxy of GaN layers directly on 6H-SiC(0001) Appl. Phys. Lett. 75, 944 (1999); 10.1063/1.124562Low temperature sapphire nitridation: A clue to optimize GaN layers grown by molecular beam epitaxy GaN nanocolumns of exceptional crystalline quality have been grown by molecular beam epitaxy on both silicon ͑111͒ and sapphire ͑0001͒ substrates. Reflection high energy electron diffraction produces a unique diffraction pattern for in situ verification of columnar growth. Subsequent molecular beam epitaxial overgrowth of the nanocolumns has been used to improve the quality of thin film GaN layers when compared to GaN films grown directly on sapphire substrates. Transmission electron microscopy was used to confirm the absence of threading dislocations in the selected columns. Scanning electron microscopy of overgrown material demonstrated surface morphology similar to thin films grown in the intermediate ͑Ga-rich͒ growth regime, or a pattern of densely packed hexagonal structures, depending on growth conditions. Low temperature photoluminescence ͑PL͒ spectra demonstrated a greater than two orders of magnitude improvement in PL intensity of overgrown film versus direct film growth.

Epitaxial growth of Al–Cr–N thin films on MgO(111)

“…Comparable results have been observed for nanocolumnar GaN films grown in a low surface mobility regime [36]. This again justifies the application of the Scherrer formula to calculate ξ ⊥ .…”

Mechanism for spontaneous growth of GaN nanowires with molecular beam epitaxy

“…Below this temperature the film no longer contains isolated nanowires, and by 760 1C it resembles a pitted, continuous film. There is variation from group to group on the center of the range of substrate temperatures for GaN nanowire growth with MBE [7][8][9][10][11], such that the total range of reported temperatures extends from 720 to 900 1C, but no one group has reported successful growth over a temperature range broader than 40 1C. The variation from system to system is most likely due to shifts in the growth window with variations in plasma source products, Ga flux, and temperature calibration, none of which are easily measured to high accuracy.…”

“…Specific examples of the variety of noncatalytic nucleation conditions include seeded growth [9], growth on Si (111) [10][11][12][13][14][15][16][17][18][19][20][21][22], growth on sapphire or Si (111) [1][2][3][4][5][6][7][8], growth on Si (1 0 0) [23], growth with intentional surface nitridation [10], growth with AlN buffer layers [5,24,25] and growth without AlN buffer layers [26,27]. In Fig.…”

Effect of Be‐doping on InGaN/GaN nanocolumn light‐emitting diode structures by rf‐plasma‐assisted molecular‐beam epitaxy

“…We reported the epitaxial overgrowth of continuous GaN film on GaN nanocolumns in 2002 [15], but Be was not used and the formation of dislocations was not discussed in that paper. More recently, Averett et al also reported the overgrowth of GaN nanocolumns, but the surface morphology was not smooth; many pits and facets remained at the coalescence boundary [16].…”