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  • 1
    Electronic Resource
    Electronic Resource
    Persistent photoconductivity in II-VI and III-V semiconductor alloys and a novel infrared detector (1991)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 69 (1991), S. 6701-6703 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Persistent photoconductivity (PPC) mechanisms, as well as the similarities and the differences of PPC properties in II-VI and III-V semiconductor alloys have been investigated. The potential applications based on PPC phenomenon in these two kinds of materials are discussed. We have observed that PPC induced in a II-VI mixed crystal by visible (above band gap) illumination can be quenched by long wavelength infrared radiation even at room temperature, which further supports our interpretation that PPC in II-VI mixed crystals is caused by random local potential fluctuations induced by compositional fluctuations. A newly developed infrared detector based on the PPC infrared quenching property of II-VI semiconductor alloys is also reported.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.348889
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  • 2
    Electronic Resource
    Electronic Resource
    Free excitonic transitions in GaN, grown by metal-organic chemical-vapor deposition (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 79 (1996), S. 7001-7004 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The dynamic processes of the free excitonic transitions in GaN grown by metal-organic chemical-vapor deposition (MOCVD) have been studied. The recombination lifetimes of the A and B excitons have been measured at different temperatures and excitation intensities, from which radiative recombination lifetimes of about 0.35 and 0.3 ns for the A and B excitons, respectively, have been obtained. An increase in excitation power has resulted in a drastic enhancement in the radiative decay rate as well as in the exciton photoluminescence quantum yield, suggesting the excitonic transitions may provide gain for laser actions in GaN. The high quality as well as high purity of the investigated MOCVD sample has been demonstrated by the observations of (1) the free A- and B-excitonic transitions, (2) excited states of the free excitons, (3) narrow free excitonic emission linewidths (1.7 meV at 10 K), (4) low electron concentration, and (5) high electron mobilities (∼600 cm2/V s). © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.362448
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  • 3
    Electronic Resource
    Electronic Resource
    Photoluminescence studies of band-edge transitions in GaN epitaxial layers grown by plasma-assisted molecular beam epitaxy (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 79 (1996), S. 2675-2683 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Continuous-wave and time-resolved photoluminescence spectroscopies have been employed to study the band-edge transitions in GaN epitaxial layers grown by plasma assisted molecular beam epitaxy. In addition to the neutral-donor-bound exciton transition (the I2 line), a transition line at about 83 meV below the band gap has been observed in an epitaxial layer grown under a lower plasma power or growth rate. This emission line has been assigned to the band-to-impurity transition resulting from the recombination between electrons bound to shallow donors and free holes D0, h+). Systematic studies of these optical transitions have been carried out under different temperatures and excitation intensities. The temperature variation of the spectral peak position of the D0, h+) emission line differs from the band gap variation with temperature, but is consistent with an existing theory for D0, h+) transitions. The dynamic processes of the D0, h+) transition have also been investigated and subnanosecond recombination lifetimes have been observed. The emission energy and the temperature dependencies of the recombination lifetime have been measured. These results have provided solid evidence for the assignment of the D0, h+) transition and show that the motions of the free holes which participated in this transition are more or less restricted in the plane of the epitaxial layer at temperatures below 140 K and that the thermal quenching of the emission intensity of this transition is due to the dissociation of neutral donors. Our results show that time-resolved photoluminescence spectroscopy can be of immense value in understanding the optical recombination dynamics in GaN. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.361138
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  • 4
    Electronic Resource
    Electronic Resource
    Relaxation of magnetization in Cd1−xMnxTe diluted magnetic semiconductors under illumination : 38th Annual Conference on Magnetism and Magnetic Materials (1994)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 75 (1994), S. 5734-5736 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Relaxation of thermoremanent magnetization (TRM) of Cd1−xMnxTe diluted magnetic semiconductors (DMS) in the spin-glass state have been studied under light illumination. The relaxation of TRM can be described well by a power law decay, M(t)=M(t0)t−α (t(approximately-greater-than)t0, t0∼2 s). The variations of the decay parameter α with the illumination light intensity has been measured and a relation which indicates that α is proportional to the photogenerated carrier concentration n has been observed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.355598
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  • 5
    Electronic Resource
    Electronic Resource
    Metastability and persistent photoconductivity in Mg-doped p-type GaN (1996)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 68 (1996), S. 1808-1810 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Electrical properties of Mg-doped p-type GaN grown by metalorganic chemical vapor deposition have been investigated by Hall effect and conductivity measurements. Metastability and persistent photoconductivity effects have been observed in GaN. It was found that at low temperatures, it takes several hours for the free hole concentration to reach its equilibrium value in the dark as well as in the photoexcited state, implying a bistable nature of impurities in p-type GaN. Temperature dependence of these behaviors have been studied, from which the energy barrier for free hole capture by ionized impurities as well as between the metastable and the stable states of neutral impurities have been obtained. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.116020
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  • 6
    Electronic Resource
    Electronic Resource
    Persistent photoconductivity in a two-dimensional electron gas system formed by an AlGaN/GaN heterostructure (1997)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 82 (1997), S. 1227-1230 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Persistent photoconductivity (PPC) effect associated with a two-dimensional electron gas (2DEG) in an AlGaN/GaN heterojunction device has been observed. As a consequence, the device was observed to be sensitive to light and the sensitivity was associated with a permanent photoinduced increase in the 2DEG carrier mobility and density. By formulating the PPC buildup and decay kinetics, we attributed the observed increase in the 2DEG carrier density and mobility to the photoionization of deep level impurities (DX like centers) in the AlGaN barrier material. In the PPC state, we were able to continuously vary the 2DEG carrier density in a single sample through photoexcitation and it has been found that the 2DEG carrier mobility increases almost linearly with the carrier density in the 2DEG channel. At 10 K, an electron mobility of 5800 cm2/V⋅s has been obtained in a PPC state. Implications of these observations on the device applications based on AlGaN/GaN heterojunctions have also been discussed. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.365893
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  • 7
    Electronic Resource
    Electronic Resource
    Band structure of superlattice with graded interfaces (1987)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 61 (1987), S. 624-628 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The electron-energy levels in the GaAs-Ga1−xAlxAs superlattice with finite thicknesses of interfaces between the layers, instead of sharp discontinuities across the interfaces, have been investigated. This model is more realistic for superlattices. A linearly increased (decreased) potential across the interfaces was assumed and a dispersion relation was derived to the second order of the thickness of the interface. The miniband structure, the shifting of the ground-state energy of the electron, and the effective-energy gap as functions of this thickness are presented.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.338214
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  • 8
    Electronic Resource
    Electronic Resource
    Semiconductor superlattices with periodic disorder (1988)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 63 (1988), S. 1984-1989 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: For a real superlattice, fluctuations are always presented in the period lengths. The band structure of semiconductor superlattices under the effect of this periodic disorder has been investigated in this paper. The zone center and zone edge of the first subband of electrons and holes and the effective energy gap as functions of this fluctuation have been calculated. We discuss the dependence of the band offset on this fluctuation. Our calculated results can be used to explain some of the experimental observations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.341098
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  • 9
    Electronic Resource
    Electronic Resource
    Lattice relaxed impurity and persistent photoconductivity in nitrogen doped 6H-SiC (1992)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 61 (1992), S. 2048-2050 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The impurity properties in n-type N doped single crystal 6H-SiC semiconductors have been studied by conductivity measurements. A slow decay of the dark current and persistent photoconductivity (PPC) have been observed at low temperatures. Different energy barriers have been obtained at different conditions. Measured donor binding energy, the electron capture barrier, and the emission barrier are 34.6±1.0, 14.9±0.3, and 45.6±1.2 meV, respectively. Our results suggest that PPC in SiC has a similar origin as that in AlxGa1−xAs. However the amount of lattice relaxation in SiC is much smaller compared with that in AlxGa1−xAs. Experimental results reported in this letter will help to understand the properties of lattice relaxed impurities. It also explains why different energy levels have been obtained previously by different methods.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.108328
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  • 10
    Electronic Resource
    Electronic Resource
    Low-temperature epitaxial growth and photoluminescence characterization of GaN (1994)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 65 (1994), S. 2317-2319 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Epitaxial layers of GaN on sapphire substrates have been grown by metalorganic chemical-vapor deposition at a deposition temperature as low as 400 °C, which is the lowest temperature for successful epitaxial growth of GaN by any technique. This is achieved by controlling the low flow rate of the source gases and by first depositing an AlN buffer layer at 400 °C. Low-temperature photoluminescence measurements have been employed to study the optical properties of the films deposited at different temperatures. © 1994 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.112729
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