摘要:

We report a systematic study of the effective mass of two‐dimensional (2D) holes in a series of tenp‐type GaAs/In0.20Ga0.80As/GaAs quantum well structure samples. The 2D hole density and its effective mass (m*)are independently determined from Shubnikov–de Haas and cyclotron resonance measurements at 4.2 K. We find them* increases from (0.123±0.005)meto (0.191±0.015)meas the 2D hole density is varied from 0.54×1011/cm2to 8.5×1011/cm2. The experimental data are described quantitatively in terms of a two‐band tight binding model using the valence band edge mass and strain‐induced valence band splitting as parameters. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.115092

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Inverted, staggered thin‐film transistors (TFTs), in which thea‐Si:H layer is deposited stepwise, using different rf powers, were prepared and studied. Using identically prepared top and bottom interface silicon layers, the multilayera‐Si:H TFT characteristics can be better or worse than those of a single‐layera‐SiH TFT, depending on the rf power used to deposit the middle layer and the total number of layers added. The result can be explained by considering the mechanism of the SiH4plasma deposition process. For example, the extra hydrogen generated in the high power plasma can passivate dangling bonds, which enhances the transistor performance. The high intensity plasma radiation source can generate defects at the film/film interface as well as in the bulk of the film, which deteriorates the transistor. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.115093

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

In this letter we report a nanoparticle‐derived route to CdTe thin films. CdTe nanoparticles 39±8 A˚ in diameter, prepared by an organometallic route, were characterized by x‐ray diffraction, UV‐Vis spectroscopy, transmission electron microscopy, and energy dispersive x‐ray spectroscopy. CdTe thin‐film deposition was realized by spraying a nanoparticle/butanol colloid onto SnO2‐coated glass substrates at variable susceptor temperatures. The resultant CdTe films were characterized by atomic force microscopy, x‐ray diffraction, and UV‐Vis spectroscopy. Smooth and dense CdTe thin films were obtained using growth temperatures ∼200 °C less than conventional spray pyrolysis. A growth temperature dependence upon CdTe grain size formation and crystallinity was observed by atomic force microscopy and x‐ray diffraction. UV‐Vis characterization revealed a transformation in the optical properties of the CdTe thin films as a function of growth temperature. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.115094

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

We provide direct and unambiguous experimental spectroscopic evidence for the structure of a switching oxide trap in thermally grown SiO2gate oxides on Si. Switching oxide traps can ‘‘switch’’ charge state in response to changes in the voltage applied to the gate of a metal‐oxide‐semiconductor field‐effect transistor. Electron spin resonance measurements reveal that someE&ggr;′centers (a hole trapped at an oxygen vacancy) can behave as switching oxide traps. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.115095

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Nanocrystalline germanium films containing erbium were deposited by thermal evaporation under 0.6 Torr of argon onto crystalline silicon wafer substrates. Weak broad photoluminescence (PL) around 1.5 &mgr;m was observed at room temperature. Annealing under 10−7Torr of vacuum for 3 h at 500 °C produced no change in the PL spectrum. After 1 h oxidation in air at 500 °C the PL intensity increased by an order of magnitude with reduction of the spectral linewidth and appearance of distinct structures, a portion of which is similar to that observed for Er‐implanted Si:O. Subsequent increase in oxidation time reduced the PL intensity slightly with no change in the spectral shape. The PL intensity exhibits a sublinear increase with pump power and approaches saturation at 200 mW. Raman spectra before and after anneal are also presented. Annealing increased the average grain size from 5 to 10 nm. The PL spectrum of erbium metal after oxidation in air at 500 °C is quite different from that of these oxidized Ge:Er films. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.115096

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

The step topography of 4°‐misoriented Si(001) surfaces was examined by scanning tunneling microscopy and spot profile analyzing–low‐energy electron diffraction. The clean Si(001)‐(2×1) surface proves to be a single domain substrate, which is characterized by a regular array of double steps. This step structure is changed dramatically upon adsorption of submonolayer quantities of Ag at ∼700 K. In this case, the formation of multisteps with fourfold, sixfold, and eightfold step heights occurs. The single domain character of the substrate is preserved, now showing a Ag‐induced (3×2) reconstruction. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.115097

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

We investigated the pressure behavior of yellow luminescence in bulk crystals and epitaxial layers of GaN. This photoluminescence band exhibits a blueshift of 30±2 meV/GPa for pressures up to about 20 GPa. For higher pressure we observe the saturation of the position of this luminescence. Both effects are consistent with the mechanism of yellow luminescence caused by electron recombination between the shallow donor (or conduction band) and a deep gap state of donor or acceptor character. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.115098

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

An accurate correspondence between the local optical responses and the structures of semiconductor light‐emitting devices is demonstrated by using an illumination‐mode photon scanning tunneling microscope with noncontact atomic force microscope technique. We study the novel‐structured lateralp‐njunctions grown on patterned GaAs(111)A substrate. Measuring the spatially resolved photoluminescence spectra with a 200 nm apertured probe, we precisely determine the position and the width of the transition region ofp‐njunctions. The illumination‐collection hybrid mode is also employed to map the two‐dimensional emission efficiency with higher resolution, which is not affected by carrier diffusion. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.115099

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

This study addresses the formation of roughness and near surface defects on Si(100) surfaces that are exposed to a remotely excited H plasma. The remote H plasma processing can be employed forinsituwafer cleaning. Atomic force microscopy, transmission electron microscopy, and residual gas analysis are used to measure the surface roughness, the near surface defects, and the etching, respectively. For remote H plasma exposures at substrate temperatures ≤300 °C, etching is observed along with a significant increase in the surface roughness and the formation of platelet defects in the near surface region. As the substrate temperature is increased to above 450 °C, etching is significantly reduced and no subsurface defects or increases in surface roughness are observed. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.115100

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Insituoptical reflectometry at the wavelength of 488 nm was employed to control the growth of MgZnSSe/ZnSSe Bragg mirror stacks for the blue‐green spectral region. 10‐ and 20‐period layer structures of MgZnSSe/ZnSSe were grown on GaAs (100) epilayers by molecular beam epitaxy. A room‐temperature peak reflectance of 86% was obtained for the 20‐period structure at the central wavelength of 474 nm. The results show that, in general,insituoptical monitoring of growth is a viable and simple method for real‐time layer thickness control of MgZnSSe/ZnSSe quarter‐wave stacks. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.115101

出版商:AIP    

年代:1995

数据来源: AIP