摘要:

Line‐of‐sight mass spectrometry was used to sample both stable and reactive neutral species near the walls in the downstream region of a high‐density helical resonator Cl2plasma during etching of Si. In this region, where the positive ion density is 1–2×1011cm−3, the Cl2number density at a pressure of 8 mTorr decreases by about 20% when the plasma is ignited. At constant pumping speed, this percentage increases with decreasing pressure, reaching 30% at 1 mTorr. A decrease of about 10% is due to expansion of the gas, heated by the plasma to a measured temperature of 400±50 K, integrated over a distance of one mean‐free path from the wall. This, therefore, accounts for about one‐half to one‐third of the drop in Cl2number density. The remaining half to two‐thirds of the decrease in Cl2number density upon ignition of the plasma can be ascribed to the formation of Cl atoms and SiClxetch products. Cl atoms are detected throughout this pressure range; their percentage increases at the higher pressures at constant pumping speed. SiCl4is the main etching product in the chamber, though not necessarily a primary product. Smaller amounts of SiCl2and possibly SiCl are also present in the plasma. Within experimental error, chlorine mass balance is found at all pressures, indicating an overall consistency in the mass spectrometric calibration methods. The percent dissociations measured in this study are much higher than earlier values derived from Cl‐atom measurements, and are more in line with recent measurements and model predictions for high‐density plasmas. Relationships between the mass spectrometer geometry and detection efficiency were also investigated. The detection configuration with the quadrupole axis perpendicular to the line of sight was found to be superior to one in which the quadrupole axis was parallel to the line of sight. In the latter configuration, signals from Cl and Cl2are anomolously large due to charge exchange, producing a collimated beam of fast neutrals at the sampling orifice. ©1996 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.362613

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

The missing correlation between film characteristics anda‐Si:H‐basedp‐i‐nsolar cells is still a controversial subject. The authors present a new parameter &mgr;0&tgr;0, evaluated from steady‐state transport measurements ona‐Si:H layers, which can indeed relate film quality and cell performance as far as the latter is limited by the quality of the intrinsic ⟨i⟩ layer. Thereby, two specific features of the evaluated &mgr;0&tgr;0product can explain its successful role as a quality parameter fora‐Si:H: First, the computation of &mgr;0&tgr;0takes into account the effects of the prevailing dangling bond occupation, which is very different in uniform films as compared to the occupation profile prevailing through theilayer of ap‐i‐nsolar cell; second, the evaluated &mgr;0&tgr;0product combines information about band mobility and defect density; furthermore it avoids some of the well‐known pitfalls of usual deep defect density measurements such as constant photocurrent method and photothermal deflection spectroscopy. Experimental data on a series of layers andp‐i‐nsolar cells illustrates the determination of &mgr;0&tgr;0in a given practical case and its successful correlation with cell efficiency. In this context, an estimation for the ratio of charged to neutral capture cross sections &sgr;±/&sgr;0of around 50 is found. ©1996 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.362614

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

The intersubband photocurrent in photovoltaicn‐type GaAs/AlAs/Al0.3Ga0.7As double‐barrier quantum‐well infrared detectors is studied as a function of the applied external voltage and the incident wavelength. The photoresponse shows a significant photovoltaic behavior, resulting from a dopant segregation process during the growth. For an externally applied bias voltage, which compensates the built‐in field, we find a multiple sign change of the photocurrent for varying incident wavelengths. A simulation of the wave functions indicates that this multiple sign change can be attributed to the coupling between the second subband in the GaAs quantum well and the subbands which are localized in the Al0.3Ga0.7As region. ©1996 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.362615

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

The effects of a thermal cycle annealing (TCA) process on the defects in GaAs and AlxGa1−xAs solar cells on Si substrates are described in this paper. The defect density is reduced and the solar cell efficiency is improved by TCA. The defect density and the solar cell efficiency are evaluated in detail with respect to TCA temperature and Al composition. The problems involved in the fabrication of a high efficiency AlGaAs solar cell on a Si substrate are discussed. ©1996 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.362616

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

We measured energy distributions of negative ions at the grounded electrode of an oxygen parallel‐plate rf discharge. Negative ions are generated in the plasma sheath in front of the rf electrode, are accelerated away from the driven electrode, and can be detected at the grounded electrode. The maximum energy of the negative ions corresponds to the negative self‐bias voltage of the rf electrode. Structures in the energy distribution reflect sheath properties and characteristics of the ion generation processes. ©1996 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.362569

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

We have measured the temperature dependence of the resistivity of alloys of the palladium–molybdenum and palladium–tungsten systems between 10 and 300 K. These alloys exhibit a decrease in electrical resistivity after deformation, contrary to the expected increase due to increased scattering from dislocations. It is shown that these changes are associated with significant alterations in electronic structure brought about by changes in atomic configuration in the lattice. ©1996 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.362570

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

Deep‐level transient spectroscopy has been combined with ion implantation in low‐temperature investigations of deep centers in silicon. We demonstrate that thermal radiation, originating from vacuum chamber walls, can influenceinsiturecording of emission rates significantly. As an example, the emissivity (en) of the hydrogenE3′ center was found to be dominated by an optical contribution at temperatures below ≊65 K. A typical value,en(op)≊5.5 s−1, has been recorded in measurements with unshielded Au Schottky diodes. This effect of thermal radiation vanishes when a diode is fully encapsulated and thereby in thermal equilibrium with the radiation field. The optically induced emissivity is particularly large for the hydrogen center used here to illustrate the effect but has been observed for other deep centers as well. ©1996 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.362571

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

The variations of refractive index with temperature, i.e., the thermo‐optic coefficients (dn/dT), are analyzed critically by use of a physical model for some important semiconductors to find the refractive index at any operating temperature for any wavelength throughout the transmission region. This model is based on three physical parameters—the thermal‐expansion coefficient and two optical band gaps, such as excitonic and isentropic that are lying in the UV region, instead of considering any empirical equations. ©1996 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.362572

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

High spatial resolution time‐resolved photoluminescence has been used to study GaInAs/GaInAsP quantum‐well structures selectively intermixed using the pulsed photoabsorption‐induced disordering technique. Photoluminescence decay measurements at wavelengths ≳1.3 &mgr;m were obtained using novel high‐efficiency photon‐counting detectors and were found to correlate spatially with the observed luminescence blue shift in these structures. Results indicate a reduction in the nonradiative recombination time of nearly two orders of magnitude as a result of this intermixing technique. ©1996 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.362573

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

In this communication we show that we can distinguish the absorption of a single quantum well from that of the substrate in a quantum well structure by using photothermal deflection spectroscopy (PDS). This technique uses the phase of the PDS signal, in addition to the amplitude. The method is applied to single and multiple quantum wells grown on InP substrates. ©1996 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.362574

出版商:AIP    

年代:1996

数据来源: AIP