摘要:

Hologram decay results are presented concerning a time varying decay rate which can be explained on the basis of a time dependent conductivity given by &sgr;=&sgr;0+&sgr;1 exp(−t/&tgr;T). An analysis based on this assumption describes the data well, giving strong support for the existence of a persistent photoconductivity component during decay. The effective time constant &tgr;eff? ln&eegr;/∂t)−1is dicsussed in terms of this component and the dark conductivity.

ISSN:0021-8979    

DOI:10.1063/1.328239

出版商:AIP    

年代:1980

数据来源: AIP

摘要:

The photogeneration of holes in aggregate photoreceptors has been investigated as a function of electric field, temperature, and excitation wavelength. The experimental results are describable by the Onsager theory. The fraction of absorbed photons that produce thermalized electron‐hole pairs is 0.58 and is independent of wavelength and temperature. At room temperature, the pair separation distance is 44 A˚. This distance is independent of wavelength and increases linearly with temperature. It is concluded that the photogeneration of free carriers can be explained by the surface dissociation of a thermalized exciton.

ISSN:0021-8979    

DOI:10.1063/1.328240

出版商:AIP    

年代:1980

数据来源: AIP

摘要:

Trans:(CH)x:n‐CdS heterojunctions have been fabricated and used to study the properties of undopedtrans‐polyacetylene. TheI‐Vdata show rectifying behavior characteristic of ap‐njunction diode, thus confirming that as‐grown polyacetylene isptype. FromC‐Vcharacteristics we infer a residual acceptor concentration in as‐grown films ofp‐(CH)xofNA?2×1018cm−3. Depletion has been studied in the polymer by using CdS of different doping concentrations. Detailed studies of the photovoltaic response at energies belowEgfor (CH)ximply the existence of a meta‐stable deep trap in the polymer with energy near the center of the gap. The threshold energy for pumping into this level provides an independent measurement of the energy gap,Eg=1.45 eV.

ISSN:0021-8979    

DOI:10.1063/1.328241

出版商:AIP    

年代:1980

数据来源: AIP

摘要:

The ’’diode’’ equation, which describes the behavior of the Cu2S/CdS solar cell, was derived from the first principles. The key results are the independence of theVocfrom the field in CdS and an explanation of the intersection of the dark and illuminated portions of theI‐Vcurves. The limiting factors and correlation with experimental results are discussed.

ISSN:0021-8979    

DOI:10.1063/1.328242

出版商:AIP    

年代:1980

数据来源: AIP

摘要:

An extended investigation has been made of the electrical and photovoltaic properties of heterojunctions prepared by spray‐pyrolysis deposition of thin ZnO films on single‐crystalp‐type CdTe. The principal experimental variables were the substrate temperature and the postdeposition temperature for annealing in H2. Under actual sunlight the optimum cell showed an open‐circuit voltage of 0.54 V, a short‐circuit current of 19.5 mA/cm2, and a solar efficiency (referred to the active area) of 8.8%, the highest value obtained to date for an authentic heterojunction on CdTe. The nature of the forward transport mechanism has been investigated, and a tunneling model in which bulk and interface deep traps control the forward characteristics is shown to provide good correlation with the experimental data.

ISSN:0021-8979    

DOI:10.1063/1.328243

出版商:AIP    

年代:1980

数据来源: AIP

摘要:

The existence of dipole layers at the metal‐insulator interface or dipole layers in the bulk of the insulator can play an important role in determining electrical conduction and dielectric loss in insulators, and the nature of the barrier to electron injection into the insulator. The conventional analysis of metal‐SiO2‐semiconductor (MOS) structures is extended to include the effect of dipoles on capacitance‐voltage (C‐V) characteristics. The occurrence of both dipole layers and trapped charge can be established by measuring the flat‐band voltage of MOS capacitors as a function of oxide thickness. Such measurements are suitable for measuring changes in the work function at the metal‐insulator interface due to metal‐insulator reaction.C‐Vmeasurements of Au‐SiO2‐Si capacitors are combined with thermally stimulated ionic conductivity (TSIC) measurements of Na+in SiO2to show that annealing of the Au‐SiO2interface between 150° and 250 °C produces a positive dipole at the Au‐SiO2contact while annealing between 250° and 400 °C results in a negative dipole at the Au‐SiO2interface as well as introducing negative charge into the insulator.C‐Vmeasurements give the magnitude of work function changes while TSIC measurements show that the changes occur at the Au‐SiO2interface. Annealing the Al‐SiO2interface at 400 °C in nitrogen or forming gas produces a dipole layer that increases the Al‐SiO2barrier height by about 0.2 eV. The work function at the metal‐insulator interface is not a well‐defined constant but depends on metal‐insulator interactions that depend, in turn, on processing of the interface.

ISSN:0021-8979    

DOI:10.1063/1.328244

出版商:AIP    

年代:1980

数据来源: AIP

摘要:

We present an alternative to conventional finite difference solutions to the transport equations for electrons and holes in nondegenerate semiconductor devices. The equations are solved using piecewise analytic methods in which the electric field is approximated by a linear function in a series of relatively large subintervals, and the continuity and current density equation is solved by transforming it into Weber’s equation. Carrier concentrations are expressed as a linear combination of Weber parabolic cylinder functions in each interval. Selfconsistency is obtained by iterative corrections with Gummel’s method. Computational results are presented for an abruptP‐N+junction. It is believed that this method is particularly efficient for moderate bias conditions and especially in modeling heterojunction solar photovoltaic devices.

ISSN:0021-8979    

DOI:10.1063/1.328245

出版商:AIP    

年代:1980

数据来源: AIP

摘要:

The forward and reverse current‐voltage characteristics of amorphous siliconp‐njunction diodes are presented as a function of doping level. A study of the forward characteristics with temperature show that at high doping levels the current is limited by tunnelling through the depletion region via gap states. At the lowest doping levels the diode current is determined by generation‐recombination in the depletion region. A similar interpretation is applied to the reverse characteristics. These results are relevant to the use of these diodes both as nonlinear elements in matrix‐addressed large‐area liquid‐crystal displays and thin‐film solar cells.

ISSN:0021-8979    

DOI:10.1063/1.328246

出版商:AIP    

年代:1980

数据来源: AIP

摘要:

Using photostimulated transient current measurements, the charge transport mechanism involved in the imaging process of particle migration microfilm has been elucidated. It was found that the illumination of a microfilm, across which an electric field had been applied, results in photogenerated electron‐hole pairs which separate within the Se particles followed by charge injection out of the particles across the Se‐styrene hexylmethacrylate interface. This injection results in negatively charged Se particles due to the more efficient transfer of holes relative to the electrons. The excitation spectrum of the Se spheres within the microfilm reflects the photoresponse of bulk amorphous Se which agrees with the photographic sensitivity of the particle migration microfilm.

ISSN:0021-8979    

DOI:10.1063/1.328247

出版商:AIP    

年代:1980

数据来源: AIP

摘要:

Intentional perturbations applied to the growth parameters of Sn‐doped GaAs layers grown by molecular beam epitaxy have been performed in order to investigate the tin incorporation mechanism. The start, the interruption, and the end of growth as well as a variation of fluxes or substrate temperature have been studied, using either the Auger electron spectroscopy (AES) measurement of tin accumulation on the surface, orC‐Vderived free‐carrier concentration profile versus any of these growth parameters. The theoretical model proposed by Wood and Joyce, based on a time‐delayed incorporation mechanism, has been found to fit the observed results, especially for As‐rich surface, provided that an incorporation mechanism of second order is assumed. For Ga‐rich conditions (Ts≳580 °C), a new result has been recognized, i.e., a significant reduction of carrier concentration asTsis increased. The assumption of a partially acceptor nature of tin incident atoms under these growth conditions does not seem to fully explain this result. On the other hand, this may be better understood assuming a certain amount of tin atoms being re‐evaporated in the high substrate temperature range. This behavior induces a temporarily weaker accumulation at the surface, and hence a relatively smaller incorporation rate.

ISSN:0021-8979    

DOI:10.1063/1.328248

出版商:AIP    

年代:1980

数据来源: AIP