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Hydrogen diffusion is investigated in boron-doped diamond from the redistribution profiles under thermal annealing of an initial step-like profile of (B,H) pairs located in a shallow region below the surface. For boron concentrations in the range 2×1019–1×1020 cm−3, the profiles are Gaussian-like and effective diffusion coefficients can be calculated. From the diffusion activation energy, we deduce a (B,H) pair dissociation energy of 2.5 eV. For lower boron concentrations, the redistribution of hydrogen is inhibited by the presence of deep traps for hydrogen which might be associated with structural defects. [Copyright &y& Elsevier]

The incorporation of hydrogen in n-type diamond has been investigated through its non-intentional introduction during the growth and through post-growth diffusion experiments. In the first case, (111) n-type diamond homoepitaxial films doped with phosphorus have been grown by microwave plasma chemical vapor deposition from a CH4+D2 mixture. The phosphorus concentrations were in the range 1.3×1018–3×1019 cm−3. The concentration of deuterium incorporated is usually 100 times below the phosphorus concentration, which indicates an absence of donor passivation by hydrogen in these films. These D concentrations are well below the H concentration of 1021 cm−3 reported in undoped (111) homoepitaxial diamond films. Exposures of phosphorus-doped and of nitrogen-doped diamonds to deuterium plasma show an absence of deuterium diffusion, even at elevated temperatures (1000 °C). The high migration energy of H−, combined with strong H-donor interactions and self-trapping of hydrogen, are possible reasons for the absence of significant hydrogen diffusion. In natural type Ia diamonds, a hydrogen-related vibrational band is very frequently observed at 3107 cm−1. From the similarity of some properties of this band and of the bands related to well identified (H, impurity) complexes in conventional semiconductors, we propose that (N,H) complexes are responsible for this absorption band. [Copyright &y& Elsevier]

The lack of a shallow donor in diamond with reasonable room temperature conductivity has been a major obstacle, until now, for the realization of many diamond based electronic devices. Most recently it has been shown that exposure of p-type (B doped) homoepitaxial diamond layers to a deuterium plasma can result in the formation of n-type diamond with a shallow donor state (Ea=0.34 eV) and high room temperature mobility (430 cm2/V s) [Z. Teukam et al., Nat. Mater. 2, 482 (2003); C. Saguy et al., Diamond Relat. Mater. 13, 700 (2004)]. Experimental results, based on the comparison of secondary ion mass spectrometry profiles of B and D and Hall effect measurements at different temperatures are presented. They confirm the previous speculation that some deuterium related complex is responsible for the donor activity in diamond. These donors are shown to be formed in a two-step process. First, deuterium diffuses into the entire B containing layer rather slowly, being trapped by the boron acceptors and passivating them. Once all B have formed complexes, further exposure to a D plasma results in the formation of a layer that contains about twice as many D atoms as the B content. This step is the one that gives rise to the excellent n-type features observed. The most recent theoretical attempts to explain the donor state by simulations of various boron-hydrogen complexes in diamond are reviewed. [ABSTRACT FROM AUTHOR]

Abstract: In this paper, we present a study on three-terminal ballistic junction and their applications to rectifiers and MUX/DEMUX. Rectifying effect is observed up to 94 GHz at room temperature. Although THz frequency performance has been demonstrated by Monte Carlo simulation, the high impedance of the nano-device combined with the parasitic capacitances is a limiting factor. [Copyright &y& Elsevier]

The conversion of the conductivity of B-doped homoepitaxially grown diamond layers from p- to n-type upon deuteration and its reconversion to p-type following annealing is extensively studied. Several B doped samples have been converted to n-type when exposed to a deuterium plasma at approximately 500 °C. The n-type features are related to D uptake of the samples. The donors, thus formed, have an ionization energy of approximately 0.34 eV below the conduction band edge and a high RT (room temperature) mobility (up to 430 cm2/V s), as determined by Hall effect measurements as a function of temperature. In the B-doped layers that do convert to n-type upon deuteration, the D to B concentration ratio is found to be in the range of one to two. Higher D uptake (D to B ratio ≫2) must be connected to B-doped layers containing a large amount of growth defects, which trap the D. The exact nature of the donor is yet unknown. However, the reversibility of the effect and its relationship with the D concentrations suggest that deuterium is involved in the formation of some complex with B or with some other defects. [Copyright &y& Elsevier]

Hydrogen diffusion studies were performed in GaN samples with different Fermi level positions. It is shown that, at 350 °C, hydrogen diffusion is quite fast in heavily Mg doped p-type material with the Fermi level close to E[sub v]+0.15 eV, considerably slower in high-resistivity p-GaN(Zn) with the Fermi level E[sub v]+0.9 eV, while for conducting and semi-insulating n-GaN samples with the Fermi level in the upper half of the band gap no measurable hydrogen diffusion could be detected. For these latter samples it is shown that higher diffusion temperature of 500 °C and longer times (50 h) are necessary to incorporate hydrogen to appreciable depth. These findings are in line with previously published theoretical predictions of the dependence of hydrogen interstitials formation in GaN on the Fermi level position. © 2001 American Institute of Physics. [ABSTRACT FROM AUTHOR]