Asymmetric dark current and photocurrent versus voltage characteristic in the Double Barrier Quantum Wells (DBQWs) photovoltaic infrared photodetector has been studied. A model based on asymmetric potential barriers was proposed. The asymmetric potential thick barrier, which due to the Si dopant segregation during growth makes a major contribution to the asymmetrical I-V characteristic, calculations based on our model agree well with experimental results. This work also confirms the potential use of this DBQWs for infrared photodetector with large responsivity and little dark current under negative bias.
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.
Fe is still the commonly used dopant to fabricate semi- insulting (SI) InP, a key material for high-speed electronic and optoelectronic devices. High resolved absorption spectra of the internal d-d shell transitions at Fe2+ in InP and the related phonon sidebands and a series of iron related absorption lines are presented. Detailed infrared absorption study of the characteristic spectra of four zero-phonon lines (ZPLs), which are attributed to transitions within the 5D ground state of Fe2+ (3d6) on the indium site in a tetrahedral crystal field of phosphorus atoms and their temperature effects are given.
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 act as an actuator for generation of antistructure defects. Fully hydrogenated indium vacancy dissociates leaving large lattice relaxation behind, deep donors, many 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.
The influences of point defects, dislocations, and precipitates on the lattice parameter of undoped semi- insulating GaAs single crystals were analyzed. It was shown that dislocations in such crystals serve as effective gettering sites for As interstitials due to the deformation energy of dislocations. The lattice parameters of these dislocated regions remain relatively constant due to the counterbalance between lattice compression and dilation around the dislocation. Regions away from dislocations show a linear dependence of lattice parameter with As interstitial concentration. Measurements of the lattice parameter in these latter regions by the nondestructive measurement of stoichiometry technique can be used to determine As interstitial concentrations. The nonuniformity in semi-insulating GaAs results in the variation in the threshold voltages of corresponding devices.
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