Effect of Mg doping on the structural and free-charge carrier properties of InN films

Abstract

We present a comprehensive study of free-charge carrier and structural properties of two sets of InN films grown by molecular beam epitaxy and systematically doped with Mg from 1.0 Â 10 18 cm À3 to 3.9 Â 10 21 cm À3 . The free electron and hole concentration, mobility, and plasmon broadening parameters are determined by infrared spectroscopic ellipsometry. The lattice parameters, microstructure, and surface morphology are determined by high-resolution X-ray diffraction and atomic force microscopy. Consistent results on the free-charge carrier type are found in the two sets of InN films and it is inferred that p-type conductivity could be achieved for 1.0 Â 10 18 cm À3 Շ [Mg] Շ 9.0 Â 10 19 cm À3 . The systematic change of free-charge carrier properties with Mg concentration is discussed in relation to the evolution of extended defect density and growth mode. A comparison between the structural characteristics and free electron concentrations in the films provides insights in the role of extended and point defects for the n-type conductivity in InN. It further allows to suggest pathways for achieving compensated InN material with relatively high electron mobility and low defect densities. The critical values of Mg concentration for which polarity inversion and formation of zinc-blende InN occurred are determined. Finally, the effect of Mg doping on the lattice parameters is established and different contributions to the strain in the films are discussed. V C 2014 AIP Publishing LLC.

Anisotropy, phonon modes, and free charge carrier parameters in monoclinicβ-gallium oxide single crystals

“…β-Ga 2 O 3 possesses monoclinic crystal structure, and is highly anisotropic. In previous work, which included uniaxial and biaxial materials in single-layer and multiple-layer structures such as corundum [52], rutile [55], antimonite [56], pentacene [57,58], zinc metal oxides [59], wurtzite structure group-III nitride heterostructures [60][61][62][63][64][65][66][67][68][69][70], and form-induced anisotropic thin films [71], we discussed theory and applications of generalized ellipsometry in detail. In a number of recent publications we discussed the treatment and necessity of investigating off-axis cut surfaces from anisotropic crystals to gain access to all long-wavelength active phonon modes, for example in ZnO [72], and in wurtzite structure group-III nitrides [73][74][75].…”

Anomalous magnetism of superconducting Mg-doped InN film

“…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 .…”

“…Like SFs, increasing [Mg] in InN was found to form zinc-blende InN and lattice strain, owing to the growth process and size effect, elucidated by X-ray diffraction (XRD) method. 32 Therefore, XRD measurements were made to characterize the films. (0002), and the GaN(0002) buffer layer were clearly observed.…”

“…Therefore, the fact that the total decrease in the c-lattice parameters is approximately 0.007 Å reveals that the growth strain dominates the reduction of the c-lattice parameters. 32 To elucidate the possibility that Mg-doped InN is responsible for the superconductivity instead of an impurity phase, the volume fraction of the superconducting phase is estimated using a commercial QD magnetic properties measurement system (QD MPMS). The magnetizations were measured as functions of temperature, M ZFC (T) and M FC (T), in a field with a strength of 100-Oe at temperatures between 2 K and 300K, where M ZFC and M FC are the measured magnetizations of the Mg-doped InN/ GaN/Al 2 O 3 sample that was zero field-cooled (ZFC) and field-cooled (FC), respectively, as presented in Fig.…”

Anisotropy, phonon modes, and lattice anharmonicity from dielectric function tensor analysis of monoclinic cadmium tungstate

“…Generalized ellipsometry is a versatile concept 19,[44][45][46] for analysis of optical properties of generally anisotropic materials in bulk (e.g., rutile,, 41 stibnite, 43 ) as well as in multiple-layer stacks (e.g., pentacene films, 47 group-III nitride heterostructures, [48][49][50] and meta-materials [51][52][53] ). A multiple sample, multiple azimuth, and multiple angle of incidence approach is required for monoclinic CdWO 4 , following the same approach used previously for monoclinic β-Ga 2 O 3 .…”