Understanding Of Doping Mechanism Research Articles

Efficiency of volatile organic compound degradation in air using doped strontium titanate photocatalysts. Quenching experiments towards understanding of doping mechanisms

Efficiency of volatile organic compound degradation in air using doped strontium titanate photocatalysts. Quenching experiments towards understanding of doping mechanisms

Editors' Choice—Review—Theory and Characterization of Doping and Defects in β-Ga2O3

Gallium oxide (β-Ga2O3) is an emerging semiconductor with relevant properties for power electronics, solar-blind photodetectors, and some sensor applications due to its ultra-wide bandgap and developing technology base for high quality, melt-based substrate growth and thick, low-doped homoepitaxial layers. Of critical importance for the commercialization of this potentially important material is understanding of doping mechanisms in the monoclinic lattice, where two types of Ga sites and three types of O sites have been identified. A critical literature review of doping and defects of the monoclinic β-phase of gallium oxide is provided in this work. Theoretical fundamentals of both donor and acceptor doping in Ga2O3 are reviewed. Advances in doping of epitaxial Ga2O3 with a focus on molecular beam epitaxy and ion implantation are critically examined. As doping is fundamentally related to defects, particularly in this material, a review of defect characterization by optical and electrical spectroscopic methods is provided as well. P-type doping, one of the fundamental challenges for Ga2O3, is discussed in terms of first-principles calculations and ion implantation of known acceptors such as Mg and N.

Towards higher electron mobility in modulation doped GaAs/AlGaAs core shell nanowires.

Precise control over the electrical conductivity of semiconductor nanowires is a crucial prerequisite for implementation of these nanostructures into novel electronic and optoelectronic devices. Advances in our understanding of doping mechanisms in nanowires and their influence on electron mobility and radiative efficiency are urgently required. Here, we investigate the electronic properties of n-type modulation doped GaAs/AlGaAs nanowires via optical pump terahertz (THz) probe spectroscopy and photoluminescence spectroscopy over the temperature range 5 K-300 K. We directly determine an ionization energy of 6.7 ± 0.5 meV (T = 52 K) for the Si donors within the AlGaAs shell that create the modulation doping structure. We further elucidate the temperature dependence of the electron mobility, photoconductivity lifetime and radiative efficiency, and determine the charge-carrier scattering mechanisms that limit electron mobility. We show that below the donor ionization temperature, charge scattering is limited by interactions with interfaces, leading to an excellent electron mobility of 4360 ± 380 cm2 V-1 s-1 at 5 K. Above the ionization temperature, polar scattering via longitudinal optical (LO) phonons dominates, leading to a room temperature mobility of 2220 ± 130 cm2 V-1 s-1. In addition, we show that the Si donors effectively passivate interfacial trap states in the nanowires, leading to prolonged photoconductivity lifetimes with increasing temperature, accompanied by an enhanced radiative efficiency that exceeds 10% at room temperature.

Magnetic coupling and electric transport in Nb, Fe co-doped rutile TiO2 epitaxial films

High quality epitaxial rutile Ti0.95-xFe0.05NbxO2−δ (x = 0, 0.01, 0.02, 0.03) films have been grown on (110) MgF2 substrates by pulsed laser deposition (PLD) method. Detailed experimental characterizations indicate that Nb co-doping in Fe doped TiO2 gives rise to a shrink of the lattice parameter, an increase of electrical resistivity and a variation of magnetic exchange coupling. These results can be explained by the donor and acceptor co-doping effect. It is supposed that Nb, Fe co-doping in rutile will result in defect-dipole clusters which localizes the free electrons, give rise to an increase of resistivity, and transfer the ferromagnetic exchange to antiferromagnetic exchange. These complex interaction between charge carriers and oxygen vacancies may enrich our understanding of doping mechanism in oxide materials and indicate a new way to explore other novel oxide materials.

Improvement in thermoelectric properties of n-type Si 95Ge 5 alloys by heavy multi-dopants

Efforts to improve the thermoelectric efficiency of silicon–germanium alloys are discussed. These efforts are essentially focused on substantially enhancing carrier concentration levels and thus increasing the values of the power factor and the figure of merit of n-type Si 95 Ge 5 alloys materials. A combination of (P + GaP) multi-dopants is used for this purpose. Very high carrier concentration levels and high electrical power factors were obtained in hot isostatically pressed materials. The good overall understanding of doping mechanisms which has been achieved should enable optimization of the thermoelectric properties over this extended carrier concentration range.