摘要:

We present a systematic analysis of the hole transport over heterobarriers in the InGaAs(P)/InP material system. The experiments have been performed on our recently developed all-optical switching structures [C. Knorr &etal;, Appl. Phys. Lett.69, 4212 (1996)], which offer an elegant access to hole transport rates. We have varied barrier thickness, barrier height, bias voltage, and temperature. The time constants vary from 30 &mgr;s to 30 ns. Our model calculations, including all heavy and light hole subbands, show that only thermally assisted tunneling can explain both the temperature and electric field dependence of the transport rates. We have extracted the activation energies. The hole capture time is determined as250±50 fs.©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.120982

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

The blue Mg induced 2.8 eV photoluminescence (PL) band in metalorganic chemical vapor deposition grown GaN has been studied in a large number of samples with varying Mg content. It emerges near a Mg concentration of1×1019 cm−3and at higher concentrations dominates the room temperature PL spectrum. The excitation power dependence of the 2.8 eV band provides convincing evidence for its donor–acceptor(D–A)pair recombination character. It is suggested that the acceptorAis isolatedMgGawhile the spatially separated, deep donor (430 meV)Dis attributed to a nearest-neighbor associate of aMgGaacceptor with a nitrogen vacancy, formed by self-compensation. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.120983

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

CdSe quantum dots on ZnSe, grown by molecular beam epitaxy and formed during reorganization of an initially uniform film by thermal activation, are microstructurally elucidated in cross section and plan view, using transmission electron microscopy. In diffraction contrast, an almost uniform wetting layer is clearly visible. Dark contrast features with a distinctly larger extension into growth direction mark the location of quantum dots. Individual quantum dots can be identified in high-resolution imaging both by lattice expansion and contrasts arising from their strain fields. Plan-view images show the coexistence of two classes of quantum dots with an average lateral size of⩽10 nm(area density100 &mgr;m−2) and 10–50 nm(20 &mgr;m−2),respectively. The shape of the larger entities is pyramidlike. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.120984

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

We study the role that disorder plays in shaping the functional form of the optical absorption spectra of amorphous semiconductors. We find, for hydrogenated amorphous silicon, amorphous germanium, amorphous gallium arsenide, and amorphous indium phosphide, that, while the breadth of the absorption tail is a strong function of disorder, the mean energy gap is insensitive to the amount of disorder. As the disorder is decreased, the optical absorption spectra associated with these amorphous semiconductors approach well defined disorderless limits, the energy gaps associated with these limits being greater than the corresponding crystalline gaps. The physical implications of these results are discussed. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.120985

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

CdS nanoparticles exhibit size dependent optical and electrical properties. We report here the photocurrent andI–Vcharacteristic studies of CdS nanoparticle devices. A sizable short circuit photocurrent was observed in the detection range governed by the size of the clusters. We speculate on the mechanisms leading to the photocurrent and emission in these nanometer scale systems. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.120986

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

Spatially resolved photoluminescence (PL) measurements have been performed on GaAs/GaInAs/GaAlAs pseudomorphic high electron mobility transistors to determine the local temperature on both sides of the gate with spatial resolution of about 1 &mgr;m and temperature resolution better than 1 °C. This local temperature is deduced from the energy shift of one of the peaks in the PL spectra. Asymmetry in the temperature distribution between the drain and source sides is observed. The experimental temperature values have also been compared with predictions from an analytical model to determine the thermal resistance in these devices. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.120987

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

We report the observation of spin relaxation of excitons in zero-dimensional semiconductor nanostructures. The spin relaxation is measured in InGaAs quantum disks by using a polarization dependent time-resolved photoluminescence method. The spin relaxation time in a zero-dimensional quantum disk is as long as 0.9 ns at 4 K, which is almost twice as long as the radiative recombination lifetime and is considerably longer than that in quantum wells. The temperature dependence of the spin relaxation time suggests the importance of exciton–acoustic phonon interaction. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.120988

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

We report simple porous silicon-based devices producing stable electroluminescence (EL) by the deposition of a poly-4-dicyanomethylene-4H-cyclopenta[2,1-b:3,4-b′]dithiophene monolayer (PCDM) into the nanostructure. The structure of these devices is Au/PCDM/porous silicon/Si/Al. The EL emission is bright, visible by the naked eye under normal daylight, and broad in wavelength, covering the whole visible range with a peak at 650 nm. The emission area of the devices is1 cm2.The EL starting voltage is in the range of 14–30 V and the current is around 300 mA. The time stability was good for all the devices tested. After exposure to the air for more than three months, the devices show nearly the same emission intensity without increase of external power supplied. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.120989

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

The relationship between the photoluminescence (PL) intensity due to the W (orI1) center and the oxygen concentration in implanted silicon crystals was studied. The PL intensity of the W center decreased consistently with increasing oxygen concentration for carbon-implanted samples with a wide range of carbon fluences, while it showed no dependence on the oxygen concentration for samples implanted with elements such as hydrogen, silicon, and heavy metals. Based on these results and considerations of the reactions of intrinsic defects generated by implantation, the origin of the PL W center was attributed to a defect composed of silicon self-interstitials. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.120990

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

We describe the use of chemically assisted ion beam etching to realize smooth, highly anisotropic features in GaSb. The measured etch rates are comparable to those of GaAs, and are fitted to a model that assumes the formation of trichloride etch product species. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.120570

出版商:AIP    

年代:1998

数据来源: AIP