摘要:

The junction capacitance for a carbonaceous thin‐film/n‐type silicon layer photovoltaic cell made by chemical vapor deposition of 2,5‐dimethyl‐p‐benzoquinone on a silicon substrate at 500 °C was measured, and an energy band diagram for this junction was sought out. The result confirms that the carbonaceous thin‐film/n‐type silicon junction is a heterotype junction. Its junction barrier is about 0.54 eV. This junction shows a depletion layer of about 1.1 &mgr;m in thickness at zero bias voltage, and most all of which was established in the silicon substrate. A work function of about 5.0 eV for the carbonaceous film was estimated based on the energy‐band diagram of this junction. ©1996 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.116833

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

We report the fabrication of an 11.6% efficient, polycrystalline thin‐film CdS/CdTe solar cell in which both semiconductor layers were deposited by planar‐magnetron‐radio‐frequency sputtering at 380 °C on commercially available soda‐lime float‐glass substrates coated with SnO2:F. We show that the magnetron magnetic field is critical to obtaining high cell efficiency. Much stronger photoluminescence and higher electrical conductivity are found in films and cells grown with unbalanced‐field magnetrons. The magnetic field dependence is interpreted as arising from the enhanced electron and ion bombardment of the film growth interface when unbalanced magnetrons are used. ©1996 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.116834

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

Luminescent films of porous silicon were obtained by laser ablation of crystalline silicon. The spectral and temporal characteristics of light emission from laser ablated porous silicon (LAPS) films critically depend on the chemical composition of the atmosphere in which they were fabricated. Luminescent characteristics, spatial structure, and chemical composition of LAPS were compared with the properties of porous silicon obtained by a standard electrochemical method on the same silicon substrate. ©1996 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.116835

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

Electroreflectance is applied to study the interface properties of metal/SiO2/GaAs structures. From a bias‐voltage dependence of surface potential, which was evaluated from the measured surface field ini/n+‐GaAs structures, energy distributions of interface‐state density were determined based on the modulation spectroscopy technique. Upon biasing toward inversion, a strong pinning of surface Fermi level occurred at around 0.88 eV below the conduction‐band minimum. This pinning, thus, is concluded to be due to a large number of interface states, and not due to an actual hole inversion. The method is free from numerical ambiguities encountered in capacitance‐based techniques, in which the energy reference for surface Fermi level is model dependent, and thus, is a suitable tool for studying insulator/semiconductor interfaces, even having a large number of interface traps. ©1996 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.116836

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

Accurate measurements of the InP refractive index as a function of free‐carrier doping are reported at 1.3 and 1.5 &mgr;m, the two strategic wavelengths for optical communications. A total of 21 samples with differentN‐ andP‐doping levels have been measured using a novel and simplified grating‐coupling technique. In contrast to the conventional method, this only involves the use of a directly etched diffraction grating on the sample surface, thereby avoiding the necessity of a specific guiding layer. The measured index, in agreement with earlier predictions, decreases by more than 0.05 when theNdoping is increased from below 1015to about 1019electrons per cubic centimeter. This effect, however, is much less pronounced withPdoping than withNdoping. ©1996 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.116837

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

An InP/InGaAs epitaxial wafer prepared by gas source molecular beam epitaxy was directly bonded with a Si wafer in an ultrahigh vacuum chamber without exposure to the air. The photoluminescence of an InGaAs quantum well layer does not deteriorate even if it is located 100 nm from the bonding interface. In a pin structure fabricated by bonding, carriers injected to the intrinsic region by forward bias reach the interface and recombine through the recombination centers at the interface. ©1996 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.116838

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

The effectiveness of copper gettering by implantation‐induced cavities in competition with internal gettering sites in silicon was demonstrated. The cavities were formed in the near surface region by He implantation and annealing while the internal gettering sites were created in the material’s bulk by a ramped hi–lo–hi oxygen precipitation heat treatment. Ion implantation was used to controllably introduce the copper. The quantity of implanted copper was below that corresponding to saturation of solution throughout the wafer at the gettering temperatures of 700 and 800 °C. The cavities were found to be an effective gettering site in the presence of internal gettering sites with only a small amount of copper being gettered at the internal gettering sites. These results have important implications for optimal gettering of metallic impurities from integrated circuit device regions. ©1996 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.116839

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

We present a technique for using modulated electroabsorption measurements to determine the built‐in potential in semiconductor heterojunction devices. The technique exploits a simple relationship between the second‐harmonic electroabsorption signal and the capacitance of such devices. We apply this technique to hydrogenated amorphous silicon (a‐Si:H)‐based solar cells incorporating microcrystalline Sip+layers. For one set of cells with a conventional plasma‐deposited intrinsic (i) layer we obtain a built‐in potential of 0.98±0.04 V; for cells with anilayer deposited using strong hydrogen dilution we obtain 1.25±0.04 V. We speculate that interface dipoles between thep+andilayers significantly influence the built‐in potential. ©1996 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.116840

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

Organic field‐effect transistors that employ copper phthalocyanine (Cu–Pc) as the semiconducting layer can function asp‐channel accumulation‐mode devices. The charge carrier mobility of such devices is strongly dependent on the morphology of the semiconducting thin film. When the substrate temperature for deposition of Cu–Pc is 125 °C, a mobility of 0.02 cm2/V s and on/off ratio of 4×105can be obtained. These features along with the highly stable chemical nature of Cu–Pc make it an attractive candidate for device applications. ©1996 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.116841

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

We have investigated the saturation of intersubband absorption and the intersubband relaxation time in the valence band of Si/SiGe quantum wells. The quantum wells consist of 3 nm thickp‐doped Si0.8Ge0.2layers separated by 20 nm thick silicon barriers. At room temperature, these quantum wells exhibit intersubband absorption inppolarization (component of the electric field parallel to the growth axis), which peaks around 130 meV (≊10 &mgr;m). The saturation of intersubband absorption has been investigated using a picosecond free electron laser by two different techniques. The intersubband absorption is first analyzed as a function of the pump intensity. The saturation is found to occur around 90 MW/cm2, which yields a characteristic lifetime T1≊0.7 ps. In a second set of experiments, the lifetime is determined by time‐resolved pump and probe experiments in cross polarization. The intersubband transition is pumped inppolarization and the saturated absorption is probed with a delayed beam inspolarization. An intersubband lifetime ≊0.4 ps is deduced by this technique. The saturation behavior is analyzed in terms of an inhomogeneously broadened two‐level system. ©1996 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.116842

出版商:AIP    

年代:1996

数据来源: AIP