摘要:

We investigate the room‐temperature photoluminescence of single In0.1Ga0.9As/Al0.33Ga0.67As quantum wells grown simultaneously on (100), (311)A, and (311)B GaAs substrates. The measurements, taken under both steady state and transient conditions, evidence that nonradiative (Shockley‐Read‐Hall) recombination dominates the emission of both the [100] and [311]B oriented samples at low injection levels, and is still important up to injection levels approaching those in lasers. The emission of the [311]A oriented sample is, in contrast, dominated by radiative recombination already at modest injection levels. The origin of this remarkable feature of the [311]A oriented sample is traced back to the reduced incorporation of deep recombination centers at the (311)A In0.1Ga0.9As/Al0.33Ga0.67As interface. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.114365

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Employing self‐ordered growth in convex corners of nonplanar Si substrates, SiGe quantum wires of approximately 30 nm lateral dimension were fabricated. Photoluminescence spectra of these structures are dominated by transitions originating from the quantum wires at measurement temperatures above 20 K. The energetic positions of the quantum wire transitions are in good agreement with Ge concentrations measured by spatially resolved energy dispersive x‐ray spectroscopy using a scanning transmission electron microscope. We find that the Ge concentration inside the wire is considerably lower than the nominal value for growth on planar parts of the substrate. In addition we find a pronounced gradient in the Ge concentration of the wire. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.114366

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Eu is incorporated into CaF2films grown on Si(100) by molecular beam epitaxy using elemental Eu evaporation. Eu doping as high as 4.05 at. % does not significantly degrade the surface morphology, indicating a relatively high solubility of Eu in CaF2. Photoluminescence spectra from Eu‐doped CaF2show strong blue emissions from Eu2+ions in cubic sites. The inhomogeneous broadening of the zero‐phonon line near 24 190 cm−1is reduced by ∼20% uponinsituannealing at 1100 °C. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.114367

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Monocrystalline Si1−xGexalloys may be an interesting material for infrared solar applications and dual band gap systems such as GaAs/Si1−xGex. At present, monocrystalline ingots of Si1−xGexhave been grown by the float zone (FZ) technique, but the minority carrier lifetime in the wafers is quite low. Gettering treatment by POCl8over Si1−xGexsamples brings about a substantial improvement of minority carrier lifetime, achieving values similar to FZ‐silicon wafers, that is over 200 &mgr;s in high resistivity samples if the Ge constant is below 5%. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.114368

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

A study of the current–voltage behavior of recombination current in CdTe/CdS solar cells has shown that the reverse saturation current,J0, and the diode quality factor,A, are correlated. Our better devices typically have low values of bothAandJ0. Spectral response data indicate that devices with a gradual decline in quantum efficiency beginning at about 600 nm show better performance than devices with a sharp drop at the CdS band gap of 510 nm, which is interpreted as an indication that mixing between CdS and CdTe during processing reduces the amount of recombination current at the interface. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.114369

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Electronic structures of 5, 10, 15, 20‐zinctetraphenylporphyrin (ZnTPP)/metal (Au, Ag, Al, Mg) interfaces prepared in ultrahigh vacuum were investigated by ultraviolet photoelectron spectroscopy (UPS). We found that the electronic energy levels of ZnTPP align to the vacuum level of substrate metal, with a constant energy shift of vacuum levels across the interface. These findings cannot be explained by the simple models assuming vacuum level alignment at the interface. We also found that sample exposure to oxygen induces energy level shift in close relation with change of substrate work function at oxygen exposure. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.114370

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

The etch rates and selectivity of Si3N4over SiO2have been investigated by microwave discharging a mixture of NF3 and Cl2and flowing the resultant fluorine and chlorine atoms and interhalogenous molecules simultaneously over a silicon wafer covered with low pressure chemical vapor deposition (LPCVD) Si3N4, and a wafer covered with thermally grown SiO2. The temperature dependence of the etch rates of Si3N4and SiO2in the NF3/Cl2mixture was examined in the range from 25 to 500 °C, and the selectivity of the nitride etch over the oxide etch as well as nitride etch rate was found to increase with increasing temperature. It was also found that both etch rates and selectivities increase with NF3flow rates within the range used in this study. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.114371

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

We have studied band filling in strained InP dots grown on GaInP. Compared to quantum wells, the dots show band filling at two orders of magnitude lower optical excitation power density. We show that the emission attributed to band filling originates from the dots by using spatially resolved photoluminescence recording emission from single dots with very high spectral resolution. With time‐resolved photoluminescence spectra we follow the dynamic relaxation of the charge carriers in the dots. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.114372

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

A method involving capacitance–voltage (C–V) measurements has been used to investigate the process of high‐field domain formation in semiconductor structures with tight‐binding GaAs/AlGaAs superlattices grown by molecular beam epitaxy. Current–voltage (I–V) measurements carried out at 77 K showed two series of current oscillations associated with the sequential tunneling process as a result of the high‐field domain formation. Accumulation of electrons in the quantum wells due to the extension of the high‐field domains through the superlattice as a result of increasing bias is detected as a sharp increase in the capacitance which clearly corresponds to a sharp reduction in the current. Preliminary results of the frequency dependence of theC–Vcharacteristic corresponding to the sequential tunneling process as an effect of the high‐field domain formation are discussed. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.114373

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

We demonstrate the metalorganic vapor phase epitaxy (MOVPE) growth of AlGaAs/GaAs two‐dimensional electron gases (2DEGs) with mobilities as high as 786 000 cm2/V s at a carrier density of 3.0×1011cm−2at 0.3 K. The mobility figures of merit (&mgr;/n3/2) for these 2DEGs are the highest reported to date for MOVPE materials. These 2DEGs also exhibit the fractional quantum Hall effect (FQHE) with minima in longitudinal resistance corresponding to Landau level filling factors 2/3, 4/3, and 5/3. The temperature dependence and carrier density dependence of mobility were characterized, and the mobility was found to vary linearly with carrier density, implying that the mobility is probably limited by background ionized impurity scattering. A delta‐doped 2DEG was also compared with uniformly doped 2DEGs and was found to have a slightly higher mobility. Finally, we obtained high mobility in a coupled double 2DEG structure for 2D to 2D tunneling applications. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.114374

出版商:AIP    

年代:1995

数据来源: AIP