Adsorption of oxygen on KxC（60） studied by photoelectron spectroscopy

国家自然科学基金

The role of hydrogen in semi-insulating INP

Complexes of vacancy at indium site with one to four hydrogen atoms and isolated hydrogen or hydrogen dimer and other infrared absorption lines, tentatively be assigned to hydrogen related defects were investigated by FTIR. Hydrogen cam passivate imperfections, thereby eliminating detrimental electronic states from the energy bandgap. Incorporated hydrogen can introduce extended defects and generate electrically-active defects. Hydrogen also can acts as an actuator for creating of antistructure defects. Isolated hydrogen related defects(e.. H-2*) may play an important role in the conversion of the annealed wafers from semiconducting to the semi-insulating behavior. H-2* may be a deep donor, whose energy level is very near the iron deep acceptor level in the energy gap.

Hydrogen related defects in InP

Local vibrational modes(LVMs) in tenths of InP samples reveal clearly existence of complexes related to hydrogen. Complexes of vacancy at indium site with one to four hydrogen atom(s) and isolated hydrogen or hydrogen dimers and complexes of hydrogen with various impurities and intrinsic defects are investigated by FTIR. Especially hydrogen related complexes between various transition metals and hydrogen or hydrogen related complexes between hydrogen with point defects. New LVMs related to hydrogen will be reported in this paper. Dynamical formation mechanism of defects in the annealed nominally undoped semiinsulating InP obtained by high pressure, high temperature annealing of ultra purity materials is proposed. Hydrogen can acts as actuator for antistructure defects production. Structural, electronic and vibrational properties of LVMs related to hydrogen as well as their temperature effects are discussed.

Hydrogen related defects in neutron-irradiated silicon grown in hydrogen ambient

Isochronal thermal-annealing behavior of NTD floating-zone silicon grown in hydrogen ambient (called NTD FZ(H) Si) is presented. The dependencies of resistivity and carrier mobility on annealing temperature are determined by room-temperature Hall electrical measurements. Using infrared absorption spectroscopy, hydrogen-related infrared absorption bands evolution for NTD FZ(H) Si were measured in detail. It is demonstrated that compared with NTD FZ(Ar) Si, NTD FZ(H) Si exhibits the striking features upon isochronal annealing in temperature range of 150 similar to 650 degreesC: there appears the formation of an excessive shallow donor at annealing temperature of 500 degreesC. It is shown that the annealing behavior is directly related to the reaction of hydrogen and irradiation-induced defects. The evolution of infrared absorption bands upon temperature reflects a series of complex reaction process: irradiation-induced defects decomposition, breaking of Si-H bonds, migration and aggregation of atomic hydrogen, and formation of the secondary defects. (C) 2002 Elsevier Science B.V. All rights reserved.

Hydrogen behavior in GaN epilayers grown by NH3-MBE

Hydrogen behavior in unintentionally doped GaN epilayers on sapphire substrates grown by NH3-MBE is investigated. Firstly, we find by using nuclear reaction analysis (NRA) that with increasing hydrogen concentration the background electron concentration increases, which suggests that there exists a hydrogen-related donor in undoped GaN, Secondly, Fourier transform infrared (FTIR) absorption and X-ray photoelectron spectroscopy (XPS) reveal Further that hydrogen atom is bound to nitrogen atom in GaN with a local vibrational mode at about 3211 cm(-1) Hence, it is presumed that the hydrogen-related complex Ga. . .H-N is a hydrogen-related donor candidate partly responsible for high n-type background commonly observed in GaN films. Finally, Raman spectroscopy results of the epilayers show that ill addition to the expected compressive biaxial strain, in some cases GaN films suffer from serious tensile biaxial strain. This anomalous behavior has been well interpreted in terms of interstitial hydrogen lattice dilation. (C) 2001 Elsevier Science B.V. All rights reserved.

High-concentration hydrogen in unintentionally doped GaN

We use nuclear reaction analysis to study hydrogen in unintentionally doped GaN, and high-concentration hydrogen, nearly 10(21) cm(-3), is detected. Accordingly, a broad but intense infrared absorption zone with a peak at 2962 cm(-1) is reported, which is tentatively assigned to the stretch mode of NH: Ga complex. The complex is assumed to be one candidate answering for background electrons in unintentionally doped GaN. (C) 1998 Elsevier Science B.V. All rights reserved.

Catalytic Activation of Mg-Doped GaN by Hydrogen Desorption Using Different Metal Thin Layers

The annealing of Mg-doped GaN with Pt and Mo layers has been found to effectively improve the hole concentration of such material by more than 2 times as high as those in the same material without metal. Compared with the Ni and Mo catalysts, Pt showed good activation effect for hydrogen desorption and ohmic contact to the Ni/Au electrode. Despite the weak hydrogen desorption, Mo did not diffuse into the GaNepilayer in the annealing process, thus suppressing the carrier compensation phenomenon with respect to Ni and Pt depositions, which resulted in the high activation of Mg acceptors. For the GaN activated with the Ni, Pt, and Mo layers, the blue emission became dominant, followed by a clear peak redshift and the degradation of photoluminescence signal when compared with that of GaN without metal.