摘要:

Resonant tunneling is observed in double barrier resonant tunneling diodes with semimetallic ErAs quantum wells. Magnetic field dependence distinguishes two different resonant channels while the thickness dependence of the voltage for resonant tunneling strongly suggests that the electrons tunnel through hole states in the semimetal quantum well. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.114393

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

A thin film containing an electron donor (tetraphenyl diamine) quenches the exciton fluorescence and substantially alters the photovoltaic properties of perylene bis(phenethylimide) cells. The film causes the open circuit photovoltage to shift positive by about 450 mV relative to cells without the film. In the case of silver back contacts, the presence of the film inverts the photovoltaic effect relative to that in the absence of the film, and causes the front electrode to become more photoactive than the back. These effects are interpreted as resulting from interfacial exciton dissociation rather than from junction formation. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.114394

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

We suggest that the role of hydrogen dilution in the improvement of the quality of hydrogenated amorphous silicon germanium alloys is to alter the relative contribution of the short and long lifetime precursors to film growth which are deleterious and beneficient, respectively. In order to circumvent the preferential depletion of germane when mixed with silane, we have used low power disilane–germane discharges and thereby obtained films with an optical gap <1.5 eV having similar Urbach tail width and defect absorption, with and without hydrogen dilution. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.114395

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

We report low‐resistive Au ohmic contact for a molecular beam epitaxy grown nitrogen dopedp‐type ZnTe (p‐ZnTe:N) layer with high thermal stability, where thep‐ZnTe surface is treated by oxygen plasma and HCl solution prior to Au film deposition. C contamination and native oxide layers of ZnTe are removed by oxygen plasma and HCl treatment, respectively, from the surface. As a result, a Te‐rich layer is formed on the surface. The annealing temperature dependence of specific contact resistance is investigated. The specific contact resistance of Au ohmic contact forp‐ZnTe:N with carrier concentration of 2×1018cm−3treated by oxygen plasma and HCl solution reaches as low as 5.8×10−6&OHgr; cm2at an annealing temperature of 350 °C. This specific contact resistance value is the same as that of the reported Pd/(Pt)/Au contact forp‐ZnTe:N with carrier concentration of 3×1019cm−3, and clearly shows higher thermal stability. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.114396

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Electron paramagnetic resonance (EPR), optical absorption, and photoluminescence (PL) spectroscopy have been combined to characterize Pb‐doped ZnO ceramic powders. We observe a decrease in the 2.26 eV emission peak and a concomitant smearing of the band edges, narrowing the effective gap of the grains to ≊2 eV with increasing lead content. Both phenomena are at least in part attributed to the formation of a separate PbO‐like phase, likely residing at the grain boundaries. The free‐carrier concentration in the grains was also observed to decrease with increasing Pb content. Our EPR results suggest that this may be due to electron transfer from oxygen vacancy donors to substitutional Pb centers, acting as electron traps. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.114397

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

We investigate the growth rate of GaAs homoepitaxy on (001) just and vicinal substrates as a function of substrate temperature, feeding rate of source gases, and H2purge duration during the atomic layer epitaxy (ALE) process. The desorption of AsHx(x=0, 1, 2) on vicinal surfaces during ALE was confirmed to be the migration of adsorbed AsHxmolecules on the surface and desorption at the steps. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.114398

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Using x‐ray diffraction and transmission electron microscopy we have found that InAs1−xPxfilms deposited on InP(001) substrates with organometallic vapor phase epitaxy grow in an unusual island growth mode characterized by large strain‐dependent interdiffusion. Initially, strong intermixing occurs, producing pseudomorphic islands of intermediate composition. These grow only until some point in the relaxation process, possibly a critical value of the strain, after which islands of the intended composition begin to appear. Furthermore, both types of islands are found to penetrate deeply into the substrate. ©1995 American Institute of Physics. 

ISSN:0003-6951    

DOI:10.1063/1.114399

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

CuInSe2epitaxial films grown on (001)‐oriented GaAs substrates by molecular beam epitaxy have been characterized by means of low temperature photoluminescence spectroscopy atT=2–102 K. Distinct emission lines were observed near the band gap, and have been investigated further with varying sample temperature. An emission at 1.0386 eV (EX1) became broader with increasing sample temperature, and still remained up toT=102 K. A distinct, sharp emission at 1.0311 eV (IX1) which disappeared at a significantly lower temperature than the other peaks was observed only in films with weak donor‐related emissions. We attribute such emissions to the ground‐state free exciton [FEn=1] and exciton bound to neutral acceptor [A0,X], respectively. The band gap of CuInSe2epitaxial films was also determined to beEg=1.046 eV at 2 K using the reported exciton binding energy ofEex=7 meV. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.114400

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Narrow Ge layers embedded in Si are investigated using photoluminescence (PL) spectroscopy. With increasing layer thickness a growth mode changeover from two‐dimensional (2D) strained‐layer growth to three dimensional Stranski–Krastanov growth is observed. Additional PL lines that are redshifted with respect to the PL signal of the 2D strained layers are attributed to islands formed by three‐dimensional growth. The occurrence of these new lines is accompanied by a blueshift of the PL of the 2D layers, indicating a strong Ge diffusion from the 2D layers towards the islands. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.114401

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Writing of nanostructures on thin metal films using atomic force microscopy (AFM) was demonstrated. The writing experiments were done in a nitrogen ambient having variable humidity. Using ap‐type heavily doped silicon AFM tip, a bias voltage was independently applied between the tip and the surface of a thin chromium layer deposited on a Si(100) substrate. Protruded patterns of various shapes were formed only on the water‐adsorbed chromium surface when applying a negative bias on the tip. Their sizes were found to be dependent on the writing time, the bias voltage, and the humidity. The smallest feature size obtained is about 20 nm. From Auger electron spectroscopy (AES) analysis, the products are shown to be Cr oxides. The surface modification mechanism appears to be tip‐induced local oxidation, i.e., anodization. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.114402

出版商:AIP    

年代:1995

数据来源: AIP