摘要:

The concept of electronic doping is used to explain unexpectedly large values of the diode quality factor (exceeding two) and supralinearity which is sometimes observed in amorphous siliconp‐i‐n‐type diodes and materials, respectively. This suggests the presence of an extra set of defect states in lightly boron‐doped films with a capture rate for electrons which is much larger than that of the inherent defect states. We also report that for high‐quality undoped intrinsic layers, the photoconductivity versus intensity behavior exhibits sublinear power dependence which increases with intensity in distinct contrast to the previously reported results. We provide a self‐consistent model which is able to explain the above observations.

ISSN:0021-8979    

DOI:10.1063/1.334845

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

A glow‐discharge hydrogenated amorphous silicon/insulator heterostructure has been characterized by a range of measurements including optical absorption, temperature dependence of photo‐ and dark conductivity, internal photoemission, xerographic discharge, and spectral dependence of photoconductivity. Efficient injection of dark and photocarriers from amorphous hydrogenated silicon into, and transport through, relatively thick SiOx:N:H has been achieved. Unlike the conventional thermal oxide on Si, no significant energy barrier to injection is found in the plasma‐deposited heterostructure. The use of the structure as a potential xerographic device is demonstrated. A mobility lifetime product as high as 6×10−10cm2/V and a transport process with an activation energy of ∼0.3 eV is found for electrons in the SiOx:N:H films.

ISSN:0021-8979    

DOI:10.1063/1.334846

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

More accurate expressions for the evaluations of the trap depthEand the capture cross sectionSrelated to the thermally stimulated current process are developed. The differentT−1,T−2,T−3, andT−4dependencies ofSon the temperatureThave been considered for the slow retrapping case. In the fast retrapping case, the energyEand the product &tgr;NThave been expressed independently, where &tgr; is the lifetime of the free electron andNTthe total trap density. The calculations depend on the temperaturesTmandT1that correspond to the peak and the half‐height of the current, respectively. A new experimental method providing the determination ofTmandT1with high precision has been developed that allows extensive experimental examination of thermally stimulated current curves in high‐resistivity CdTe crystals. Application to defect parameters of fourteen levels in CdTe has been carried out in the slow and fast retrapping limits. In the slow retrapping case, the results differ from those obtained by the widely used Grossweiner formula. For the fast retrapping limit the values ofEcorresponding to different sets ofTmandT1are calculated independently of &tgr;NT. This again has not been the case published by the different authors.

ISSN:0021-8979    

DOI:10.1063/1.334847

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

Electrical conductivity and ionic transference measurements performed at varying temperatures and partial pressures of oxygen show that CALGAR (Ca3Al2Ge3O12), a luminescent garnet, is a mixed ionic‐electronic conductor. An activation energy of 1 eV for ionic diffusion is measured. An absorption band at 400 nm, whose magnitude can be controlled by varying the annealing atmosphere, is attributed to an O−center.

ISSN:0021-8979    

DOI:10.1063/1.334848

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

Optical properties and the photovoltaic effect in Pb2CrO5thin films, which are prepared by an electron‐beam evaporation technique, are investigated. From the main peaks of the x‐ray diffraction (XRD) patterns, which depend on the preparation condition, thin films are classified into three types: (1) (020), (2) (310), and (3) (200). The sample with a (310) main reflection has a similar XRD profile to that of the bulk material. A device to measure the photovoltiac response in the thin films has one pair of semitransparent Au electrodes on the same surface. All the Pb2CrO5thin films had a photovoltaic response. The (310) sample shows the largest photosensitivity. In this sample the saturation photovoltage is 1.16 V at a light intensity of 23.25 mW/cm2. The absorption constant (&agr;) of thin films in the visible region ranges between 4×103and 1×105cm−1. A band‐gap energy of 2.3–2.4 eV is obtained from both plots of &agr;2and photovoltage as a function of photon energy.

ISSN:0021-8979    

DOI:10.1063/1.334849

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

Theoretical and experimental results describing the dependence of the Seebeck and Peltier coefficients on the composition of Ga1−xAlxAs solid solution are given. The Seebeck coefficient for nondegenerately dopedn‐ andp‐type Ga1−xAlxAs is given by the simple expressions &agr;n=(k/e)(lnNc/n+2) and &agr;p=−(k/e)(lnNv/p+2), respectively. The dependence of &agr; on the composition of Ga1−xAlxAs solid solutions is linear forptype and nonlinear forntype. This relation is dependent on the type of carrier that is involved in the conduction process, as well as the detailed band structure of the material. Forp‐type material, two kinds of carriers are involved: heavy and light holes; forn‐type material, three kinds of carriers are involved: one direct electron and two indirect electrons. The direct electrons are dominant for Al composition of 0<x<0.3, and the indirect electron is dominant for composition 0.45<x<1. Experimental measurements of the Seebeck coefficient forn‐ andp‐type Ga1−xAlxAs and for AuGe and AuZn resemble the theoretical results.

ISSN:0021-8979    

DOI:10.1063/1.334850

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

The electron velocity distribution is calculated for an idealized model of the high electron mobility transistor using a many‐particle Monte Carlo model and a self‐consistent two‐dimensional Poisson solver. Hot electron effects, nonstationary effects, and real space transfer are analyzed. The results show that significant velocity overshoot, 2.8×107cm/s at 300 K and 3.7×107cm/s at 77 K exists under the gate and that the velocity overshoot is limited by bothk‐space transfer and real‐space transfer. The values of the overshoot velocities are much smaller than those obtained from the more conventional drift‐diffusion model.

ISSN:0021-8979    

DOI:10.1063/1.334851

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

The band discontinuity has been determined for a GaAs/AlGaAs heterojunction prepared by molecular beam epitaxy. The conduction band‐discontinuity &Dgr;Ecand the valence‐band discontinuity &Dgr;Evwere independently obtained by theC‐Vprofiling technique, taking into account a correction for the interface charge density. The simulation was employed to confirm the reliability of the obtained band discontinuity. The &Dgr;Ecdependence on both the Al composition of the AlGaAs layer and the heterojunction structure (AlGaAs on GaAs, or GaAs on AlGaAs) was examined. We found that &Dgr;Ecand &Dgr;Evwere determined to be 62 and 38% of the band‐gap discontinuity &Dgr;Eg, being independent of the structure.

ISSN:0021-8979    

DOI:10.1063/1.334852

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

A simple form of a buried heterostructure AlxGa1−xAs‐GaAs quantum‐well laser is described that is realized by impurity‐induced layer disordering (donor‐induceddisordering). The layer disordering [and the resulting band‐gap shift to higher energy (and lower index)] is accomplished by Si diffusion in a stripe pattern defined by a Si3N4mask. Single‐mode lasers of stripe width 3 and 6 &mgr;m are demonstrated that operate continuously at 300 K in the threshold current range of 10–25 mA and with single‐facet power levels as high as 10–20 mW.

ISSN:0021-8979    

DOI:10.1063/1.334853

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

We studied undoped GaAs films grown by metalorganic chemical vapor deposition in a vertical geometry atmospheric pressure reactor. Our results on the surface morphology, carrier concentration and conductivity type and low‐temperature photoluminescence spectra of the films, studied as a function of substrate temperature and As/Ga flux during growth, are generally in agreement with previous studies. In addition, we also report the effect of rotation speed of the substrate during growth. It is found that lower speeds give higher defect density and lessn‐type films and most notably enhance a defect exciton line at 1.5119 eV. From the free‐to‐bound transitions and from the dependence of the intensities of the exciton lines on growth temperature and As/Ga flux we inferred that the acceptors in our films are C, Zn, Mg and donors are those substituting on Ga sites.

ISSN:0021-8979    

DOI:10.1063/1.334854

出版商:AIP    

年代:1985

数据来源: AIP