Influence of high Mg doping on the microstructural and optoelectronic properties of GaN

Atomic Structure of Defects in GaN:Mg Grown with Ga Polarity

“…An expansion of the interplanar spacing along the c-axis was measured on the defect base, suggesting Mg accumulation [6]. Other researchers have observed similar types of defects and described them as inversion domain inclusions [7][8]. The latest authors [8] confirmed our earlier observation [3] that the direction from the tip to the base of this defect is always from Ga to N and parallel to the c-axis.…”

Defects in p-doped bulk GaN crystals grown with Ga polarity

“…The direction in which the vector from the Ga atom to its neighboring N atom lies along the caxis is described as [0 0 0 2] and called Ga growth polarity [11][12][13][14][15][16][17][18]. The opposite direction, from the N to Ga atom along the negative c-axis direction, ½0 0 0 2, is called N polar.…”

“…Their bases and side-walls are decorated by Mg [3] on which a small thickness of GaN has grown. Some investigators have considered these defects to be inversion domains with equal sample thickness outside and inside the defect [17,18], and others have described them as Mg 3 N 2 precipitates [21].…”

Structural Defects and Relation with Optoelectronic Properties in Highly Mg-Doped GaN

“…In the same doping range, two phenomena occur: the photoluminescence spectra of the samples begin to be dominated by an intense and broad blue band, peaking in the 2.7-2.9 eV range, and the free hole concentration begins to drop with increasing doping (auto-compensation). Based on the fact that, at inversion domain boundaries, an interfacial charge with superficial density twice the GaN spontaneous polarization (2 Â 0.029 C/m 2 ) exists, we have already shown, that the localization of minority electrons in the wells formed by the IDB-induced electric field discontinuities is sufficient to account for the energetic position of this blue luminescence band, and its variation with defect size [10]. In the following, we shall focus on the auto-compensation problem.…”