Investigation of Residual Donor Defects in Undoped and Fe-Doped LEC InP

The free electron concentration of as-grown liquid encapsulated Czochralski (LEC) InP measured by Hall effect is much higher than the concentration of net donor impurity determined by glow discharge mass spectroscopy. Evidence of the existence of a native donor hydrogen-indium vacancy complex in LEC undoped and Fe-doped InP materials can be observed with infrared absorption spectra. The concentration increase of the donor complex correlates with the increase of ionized deep acceptor iron impurity Fe~(2+) concentration in Fe-doped semi-insulating (SI) InP. These results indicate that the hydrogen-indium vacancy complex is an important donor defect in as-grown LEC InP, and that it has significant influence on the compensation in Fe-doped SI InP.

Defects in GaSb studied by coincidence Doppler broadening measurements

Undoped, Zn-doped and Te-doped GaSb with different concentrations were investigated by positron lifetime spectroscopy (PAS) and the Doppler broadening technique. Detection sensitivity of the latter technique was improved by using a second Ge-detector for the coincident detection of the second annihilation photon. PAS measurement indicated that there were vacancies in these samples. By combining the Doppler broadening measurements, the native acceptor defects in GaSb were identified to be predominantly Ga vacancy (V-Ga) related defects.

Architecture research and hardware implementation on simplified neural computing system for face identification

This paper describes a special-purpose neural computing system for face identification. The system architecture and hardware implementation are introduced in detail. An algorithm based on biomimetic pattern recognition has been embedded. For the total 1200 tests for face identification, the false rejection rate is 3.7% and the false acceptance rate is 0.7%.

Artificial neural networks expecting more advanced microelectronics technology

　

Global stability of Hopfield neural networks

This paper gives a condition for the global stability of a continuous-time hopfield neural network when its activation function maybe not monotonically increasing.

Dynamics of formation of defects in annealed InP

Dynamics of formation of defects in the annealed nominally undoped semi-insulating InP obtained by high pressure, high temperature annealing of high purity materials is proposed. Incorporated hydrogen passivates vacancy at indium site from annihilation forming fully hydrogenated indium vacancy which dissociates leaving large lattice relaxation behind, deep donors, mainly larger complexes involving phosphorus at indium site and isolated hydrogen defects are created in nominally undoped InP after annealing. Also created are acceptor levels such as vacancy at indium site. Carrier charge compensation mechanism in nominally undoped InP upon annealing at high temperature is given. Microscopic models of hydrogen related defects are given. Structural, electronic and vibrational properties of LVMs related to hydrogen as well as their temperature effect are discussed.

Formation mechanism of defects in annealed InP

Dynamical formation mechanism of defects in the annealed nominally undoped semi-insulating InP obtained by high pressure, high temperature annealing of high purity materials is proposed. Local vibrational modes in tenths of InP samples reveal clearly existence of complexes related to hydrogen. Complexes of vacancy at indium site with one to four hydrogen atoms and isolated hydrogen or hydrogen dimers, complexes of hydrogen with various impurities are investigated by FTIR. Hydrogen can acts as an actuator for generation of antistructure defects. Fully hydrogenated indium vacancy dissociates leaving large lattice relaxation behind, deep donors, mainly larger complexes involving phosphorus at indium site and isolated hydrogen defects are created in nominally undoped InP after annealing. Also created are acceptor levels such as vacancy at indium site. Carrier charge compensation mechanism in nominally undoped InP upon annealing at high temperature is given. Microscopic models of hydrogen related defects are given. Structural, electronic and vibrational properties of LVMs related to hydrogen as well as their temperature effect are discussed.

Influence of open-tube Ga diffusion on the characteristics for thyristor

Open-tube Ga diffusion into a SiO2/Si structure was used for fabrication of the high speed thyristor. The advantages of open-tube Ga diffusion are as follows; it is easier to operate and easier to control the profile of the Ga concentration during processing, a clean surface, which is free from alloy spots can be obtained, this technique ensures to improve the on-state characteristics and dynamic characteristics.

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.

Characterization of defects and whole wafer uniformity of annealed undoped semi-insulating InP wafers

Semi-insulating (SI) InP wafers of 2 and 3 in. diameters have been prepared by annealing undoped LEC InP at 930 degreesC for 80 h under pure phosphorus ambient (PP) and iron phosphide ambient (IP). The electrical uniformity of annealed undoped SI wafers, along with a Fe-doped as-grown SI LEC InP wafer, has been characterized by whole wafer PL mapping and radial Hall measurements. Defects in these wafers have been detected by photo-induced current transient spectroscopy (PICTS). The results indicated that the uniformity of IP wafer is much better than that of PP wafer and as-grown Fe-doped Si InP wafer. There are fewer traps in undoped SI InP IP wafer than in as grown Fe-doped and undoped SI InP PP wafer, as evidenced by PICTS. The good uniformity of the IP wafer is related to the nonexistence of high concentration of thermally induced defects. The mechanism for this phenomenon is discussed based on the results. (C) 2002 Elsevier Science B.V. All rights reserved.

Observation of defects in GaN epilayers

GaN epilayers grown on sapphire substrates nitridated for various lengthy periods were investigated by light scattering tomography (LST) and Raman scattering. In the LST images of the plane-view epilayers, the light scattering defects distribute in [<11(2)over bar 0>] directions. The defect density is lower in epilayer grown on substrate nitridated for a longer period. The defects are believed to be straight threading edge dislocations on {<1(1)over bar 00>} planes. The Raman shift of E-2 mode is larger in the sample grown on substrate nitridated for a longer period. Our results show that the stress is higher in the sample with fewer dislocations.