Correlation between switching to n-type conductivity and structural defects in highly Mg-doped InN

Abstract

The effect of Mg doping on the microstructure of InN epitaxial films in relation to their free-charge carrier properties has been investigated by transmission electron microscopy (TEM) and aberration corrected scanning TEM. We observe a direct correlation between Mg concentration and the formation of stacking faults. The threading dislocation density is found to be independent of Mg concentration. The critical Mg concentration for the on-set of stacking faults formation is determined and found to correlate with the switch from p- to n-type conductivity in InN. Potential mechanisms involving stacking faults and point defect complexes are invoked in order to explain the observed conductivity reversal. Finally, the stacking faults are structurally determined and their role in the reduction of the free electron mobility in highly doped InN:Mg is discussed.

Synthesis and Applications of III–V Nanowires

“…In practice for planar growth on sapphire, there is only p-type conduction realized in a doping window 3 × 10 18 to 3 × 10 19 cm –3 , at lower doping the material becomes degenerate n-type due to a dominance of shallow donors . At Mg-doping above 10 20 cm –3 , InN becomes n-type due to an abundance of structural defects (such as stacking faults) creating donors . Because of such defect-related problems in the present InN planar technology with growth on sapphire, InN devices are not well developed.…”

“…447 At Mg-doping above 10 20 cm −3 , InN becomes n-type due to an abundance of structural defects (such as stacking faults) creating donors. 448 Because of such defect-related problems in the present InN planar technology with growth on sapphire, InN devices are not well developed. There is indeed a need for development of high quality bulk InN materials for high quality substrates.…”

Anomalous magnetism of superconducting Mg-doped InN film

“…Khromove et al recently identified a strong correlation between the switch to n-type conductivity in highly Mg-doped InN and structural distortion. 31 They observed the formation of stacking faults (SFs) in an InN film with an Mg concentration of 1.8 × 10 20 cm −3 using high-resolution STEM (HRSTEM) (n-type conductivity was observed with a free charge carrier density of 9 × 10 17 cm −3 .) They authors suggested that the stacking faults (SFs) critically increase the concentration of point defects that act as donors in InN.…”

“…The nature of the conductivity of the Mg-doped InN sample is very important because it is related to its structural characteristics. 31,32 Mg concentration, [Mg], that provides for p-type conductivity in InN has been demonstrated to be in the range 1.0 × 10 18 cm −3 [Mg] 2.9 × 10 19 cm −3 . 33 Mg-doped InN becomes n-type when [Mg] exceeds 2.9 × 10 19 cm −3 .…”

“…2(a) indicates the unknown peak of the impurity phases, which may arise from the zinc-blende InN, InN (10-11) or elemental indium. 31,34,35 The volume fraction of the impurity phase, estimated as I im I InN:Mg , is around 5 %, where I im is the intensity of the unknown peak and I I n N :M g is the intensity of the InN:Mg (0002) peak. The calculated c-lattice parameter of the InN film is 5.725 Å that of the Mg-doped InN film is 5.718 Å. Xie et al have shown that increasing the Mg concentration from 10 18 cm −3 to 10 21 cm −3 reduced the c-lattice parameters by 0.02 Å and increased the a-lattice parameters by 0.02 Å by the strain generated during growth process.…”