Growth mode and surface morphology of a GaN film deposited along the N-face polar direction on c-plane sapphire substrate

Abstract

Articles you may be interested inPredominant growth of non-polar a-plane (Al,Ga)N on patterned c-plane sapphire by hydride vapor phase epitaxy J. Appl. Phys. 113, 093505 (2013); 10.1063/1.4794098 Polarity determination of a-plane GaN on r -plane sapphire and its effects on lateral overgrowth and heteroepitaxy J. Appl. Phys. 94, 942 (2003); 10.1063/1.1578530 Comparative study of GaN and AlN nucleation layers and their role in growth of GaN on sapphire by metalorganic chemical vapor depositionThe dependence of polar direction of GaN film on growth conditions has been investigated by changing either the group-V/group-III ratio ͑V/III ratio͒ in supplying the source gas or the deposition rate. GaN films were deposited on a nitrided sapphire by two-step metalorganic chemical vapor deposition. The surface morphology changed from flat hexagonal to pyramidal hexagonal facet with the increase of V/III ratio. However, the polar direction of GaN on an optimized buffer layer of 20 nm thickness was N-face (Ϫc) polarity, independent of both the V/III ratio and the deposition rate. The polarity of the GaN epitaxtial layer can be determined by that of an interface ͑nitrided sapphire, annealed buffer layer or GaN substrate͒ at the deposition of GaN epitaxial layer. The higher V/III ratio enhanced the nucleation density, and reduced the size of hexagonal facets. The nuclei, forming the favorable hexagonal facets of wurtzite GaN, should grow laterally along the ͕101 0͖ directions to cover a room among the facets until coalescence. After coalescence, Ϫc GaN growth on a flat hexagonal facet results in a pyramidal hexagonal facet. The growth mode for Ϫc GaN has been discussed with respect to surface structure and migration length of adsorbing precursors, in comparison with Ga-face (ϩc) GaN.

N-polar InGaN-based LEDs fabricated on sapphire via pulsed sputtering

“…4,5 However, metalorganic chemical vapor deposition (MOCVD) growth of N-polar GaN on sapphire typically leads to the formation of a rough surface morphology with hexagonal pyramidal structures and lower crystalline quality than Ga-polar GaN. 6 Such hexagonal hillocks were also observed in homoepitaxial GaN layers grown on N-polar GaN bulk substrates by MOCVD. 7 Moreover, the growth on N-polar faces suffers from the significant incorporation of residual impurities such as oxygen, which leads to difficulties in controlling n-type and p-type conductivities.…”

A Comparison of N-Polar () GaN Surface Preparations for the Atomic Layer Deposition of Al2O3

“…However, preparing N-polar GaN is more difficult, since the surface is more reactive. 25 To date there have been few published studies reporting the effects of different pretreatments on N-polar GaN. English et al 26 compared the surface morphology change of the N-polar GaN surface after various pretreatment method, but they did not report any the electrical properties of the ALD oxides nor did they correlate the effect of pretreatments.…”

Dependence of Polarity and Crystal Quality of the HVPE GaN Buffer Layers on the Surface Treatment of Substrates (GaAs and Sapphire)

“…It becomes generally N polarity, but it sometimes becomes Ga polarity by annealing in N 2 atmosphere or by an appropriate growth conditions [2]. Anyway, GaN grown on these buffer layer continues their polarity and never change in the MOVPE growth [3]. However, in case of the HVPE growth, we reported that the intermediate layer on the N polarity buffer layer grown on the GaAs(111)B surface showed the Ga polarity [4].…”