摘要:

Metal‐insulator‐semiconductor inversion layer (MIS‐IL) silicon solar cells are of significant interest for terrestrial solar electricity production due to their simple, energy‐saving fabrication process. In this work we present experimental results for an improved MIS‐IL silicon solar cell design based on the truncated‐pyramid concept. The cells exhibit independently confirmed 1‐sun efficiencies above 17%, by a clear margin the highest values ever reported for this promising class of photovoltaic devices. ©1996 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.116908

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

GaAs epilayers were grown with a wide range of excess arsenic concentrations and subjected to various anneals to study the role of the point defects and arsenic precipitates in carrier trapping and recombination. Prior to anneal, the point defects rapidly trap photogenerated electrons and holes—usually on subpicosecond time scales. However, full electron‐hole recombination occurs on a significantly longer time scale. After anneal, the full electron‐hole recombination lifetime appears to be greatly reduced, indicating that the arsenic precipitates play a significant role. ©1996 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.116909

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

Using molecular beam epitaxy (MBE) several layers of GaSb were grown on GaAs at substrate temperatures of 400, 475, and 550 °C, and the surface morphology was studied with aninsituultra high vacuum scanning tunneling microscope (STM). We have observed spiral mound growth of different morphology originating from surface dislocations for the samples grown at 400 and 475 °C, however at 550 °C there is no spiral mound growth and neighboring dislocations are joined by a single step. The surfaces have different rms surface roughness and dislocation density which has important consequences with regard to heterointerface quality. ©1996 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.116910

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

The plasma induced charging of surfaces in a plasma during semiconductor processing has been measured noninvasively using microelectromechanical devices. We have designed, modeled, and fabricated microcantilevers to act as charge sensing probes. The devices exhibit a mechanical deformation when charged, which is probedinsituby optical techniques, or measured by optical inspection after removal from plasma. Charging voltage measurements in a parallel‐plate reactive‐ion‐etching reactor show that more charging is evident at the electrode edge, and that the charging is a strong function of input rf power, chamber pressure, and flow rate of gases. ©1996 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.116911

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

Mg doped GaN epilayers grown by reactive molecular beam epitaxy (MBE) exhibit clear persistent photoconductivity (PPC) whose manifestation has been used to probe the nature of Mg impurities in GaN. PPC buildup and decay transients and the dependence of the PPC decay time constant on the PPC buildup time have been systematically measured and formulated in the context of lattice relaxed Mg impurities (orAXcenters). Our results have demonstrated that there is an energy barrier of about 129 meV which prevents free hole capture by ionized Mg impurities and that there is a lattice relaxation associated with Mg impurities in GaN. We also present a detailed comparison for Mg impurities inp‐type GaN epilayers grown by MBE (hydrogen‐free) and metalorganic chemical deposition (hydrogen rich). ©1996 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.116912

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

Stripe‐ and ridge‐geometry in InGaN multi‐quantum‐well (MQW)‐structure laser diodes (LDs) were fabricated on sapphire substrates with (112¯0) orientation (A face). The ridge‐geometry InGaN MQW LDs showed strong stimulated emission at a wavelength of 411.3 nm under a pulsed current injection of 199 mA at room temperature. The differential quantum efficiency per facet and the threshold current of ridge‐geometry LDs were 30% and 180 mA, respectively. The laser threshold current density was 3 kA/cm2. These values were greatly improved in comparison to those of stripe‐geometry LDs. The characteristic temperature of the threshold current was around 185 K. ©1996 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.116913

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

A comparative study of the magnetic properties of Bi2Sr2Ca1−xYxCu2O8+&dgr;single crystals with different yttrium contents is presented. An optimum in the doping can be reached that corresponds to a highTc(onset) value (91.5 K) and a high position of the irreversibility line. Moreover, the fishtail feature disappears for this optimally Y doped Bi‐2212 crystal due to the increase of the magnetic field dependence of the critical current density. This demonstrates the better pinning efficiency of the crystals with the highestTc. ©1996 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.116914

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

We report the observation of radio frequency‐superconducting quantum interference device (rf‐SQUID) effect due to natural grain boundary weak links in a bulk sample of a YNi2B2C superconductor at 4.2 K, confirming that the superconducting grains are coupled at the grain boundaries through Josephson effect. Periodic oscillations in voltage‐flux characteristic due to rf‐SQUID effect have been clearly observed at 4.2 K when the driving rf frequency was kept slightly away from the resonance frequency of the tank circuit. Phase reversal in the voltage‐flux characteristics on changing the rf frequency has been observed. Noise spectrum of the YNi2B2C bulk rf‐SQUID is also reported. ©1996 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.116915

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

In this letter we report on the growth of thick films of magnetoresistive La2/3Sr1/3MnO3films using a spray printing technique. The as‐prepared films display a room‐temperature magnetoresistance of 0.0012%/Oe in the 1 kOe field region. We will show that this field sensitivity is high enough to fabricate devices which, operated under a bias magnetic field, can be used as a sensitive and low‐cost magnetic sensors. ©1996 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.116916

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

Polarized neutron reflectometry was performed on a [Fe3O4/NiO]x15multilayer, molecular beam epitaxy grown on a (001) MgO substrate, in both exchange biased and nonexchange biased states. The Fe3O4layers exhibit a depth‐dependent magnetic profile characterized by a change in the magnetization near the Fe3O4/NiO interfaces. In the exchange biased state, measurements performed in the two saturated states of the magnetic hysteresis loop reveal magnetic differences in the Fe3O4, possibly due to the interfacial domain wall formation in the ferromagnetic layer. ©1996 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.116917

出版商:AIP    

年代:1996

数据来源: AIP