The development of radiation resistant insulating layers for planar silicon technology, 29 May 1968 - 28 June 1969
Ion implantation method for improving radiation resistance of thermal oxides on silicon
Donovan, R. P.↗
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Air Force/Ion Physics hardened lithium doped solar cell development
Introduction of lithium by ion implantation eliminates reproducibility and surface problem deficiencies of other introduction techniques. Implantation has been demonstrated to make possible a degree of control over the cell lithium content which has not previously been available. Front barrier development remains to be completed. Successful development of the barrier will make available the freedom to select optimum lithium concentration throughout the cell, including in the vicinity of the junction.
Kirkpatrick, A.↗
Development of GaAs solar cells
Calculations of GaAs solar cell output parameters were refined and a computer model was developed for parameter optimization. The results were analyzed to determine the material characteristics required for a high efficiency solar cell. Calculated efficiencies for a P/N cell polarity are higher than an N/P cell. Both cell polarities show efficiency to have a larger dependence on short circuit current than an open circuit voltage under nearly all conditions considered. The tolerances and requirements of a cell fabrication process are more critical for an N/P type than for a P/N type cell. Several solar cell fabrication considerations relative to junction formation using ion implantation are also discussed.
Mcnally, P. J.↗
Development of gallium arsenide solar cells
The potential of ion implantation as a means to the development of high efficiency gallium arsenide solar cells is investigated. Summaries are included of the results of computer calculations of GaAs cell characteristics, based on a model which includes the effects of surface recombination, junction space-charge region recombination, and built-in fields produced by nonuniform doping in the region; of the fabrication technology developed under the program; and of the results of electrical and optical measurements on the samples produced during the program. It was determined that measured AMO efficiencies were more than a factor of two lower than the calculated values.
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GaN for LED applications
In order to improve the synthesis of GaN the effect of various growth and doping parameters has been studied. Although Be, Li, Mg, and Dy can be used to overcompensate native donors, the most interesting acceptor element is Zn. The emission spectrum and the luminescence efficiency depend on the growth temperature (below 800 C), on the partial pressure of the doping impurity, and on the duration of growth. Blue-green electroluminescence with a power efficiency of 0.1 percent and a brightness of 850 fL (at 0.6 mA and 22.5 V) was obtained. Some diodes allow the color of the emitted light to change by reversing the polarity of the bias. Continuous operation of a diode over a period of 5 months showed no evidence of degradation. The luminescence properties of ion-implanted GaN were studied. Delay effects were found in the electroluminescence of diodes, although, with a dc bias, a 70-MHz modulation was possible.
Pankove, J. I.↗
Development of gallium arsenide solar cells
The potential of ion implantation as a means of developing gallium arsenide solar cells with high efficiency performance was investigated. Computer calculations on gallium arsenide cell characteristics are presented to show the effects of surface recombination, junction space-charge recombination, and built-in fields produced by nonuniform doping of the surface region. The fabrication technology is summarized. Electrical and optical measurements on samples of solar cells are included.
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Investigation of the growth of garnet films by liquid phase epitaxy
Liquid phase expitaxy was investigated to determine its applicability to fabricating magnetic rare earth garnet films for spacecraft data recording systems. Two mixed garnet systems were investigated in detail: (1) Gd-Y and (2) Eu-Yb-Y. All films were deposited on Gd3Ga5012 substrates. The uniaxial anisotropy of the Gd-Y garnets is primarily stress-induced. These garnets are characterized by high-domain wall mobility, low coercivity and modest anisotropy. Characteristic length was found to be relatively sensitive to temperature. The Eu-Yb-Y garnets exhibit acceptable mobilities, good temperature stability and reasonable quality factors. The uniaxial anisotropy of these garnets is primarily growth-induced. The system is well suited for compositional "tailoring" to optimize specific desirable properties. Liquid phase epitaxy can be used to deposit Gd3Ga5012 spacing layers on magnetic garnet films and this arrangement possesses certain advantages over more conventional magnetic filmspacing layer combinations. However, it cannot be used if the magnetic film is to be ion implanted.
Moody, J. W.↗
Effects of ionizing radiation on CCD's
The effects of 1.2 MeV gamma radiation and 20 MeV electrons on the operational characteristics of CCDs are studied. The effects of ionizing radiation on the charge transfer efficiency, dark current, and input/output circuitry are described. The improved radiation hardness of buried channel CCDs is compared to surface channel results. Both ion implanted and epitaxial layer buried channel device results are included. The advantages of using a single thickness SiO2 gate dielectric are described. The threshold voltage shifts and surface state density changes of dry, steam, and HCl doped oxides are discussed. Recent results on the recovery times and total dose effects of high dose rate pulses of 20 MeV electrons are reported.
Hartsell, G. A.↗
Measurements of lunar atmospheric loss rate
Ions from the lunar atmosphere are observed near the lunar terminators by the Apollo Suprathermal Ion Detector Experiments. These ions are accelerated toward the lunar surface by the interplanetary electric field and the lunar surface electric field. The ion implantation rates for these mechanisms are of the order of 7 and 0.4 g/sec, respectively. The removal rate into space by the interplanetary electric field is also approximately 7 g/sec. This measurement is used as a constraint to evaluate possible sources of the lunar atmosphere. Upper limits to the size of the lunar atmosphere in the past are established by computing the loss rate of denser lunar atmospheres.
Vondrak, R. R.↗
Development of methods and procedures for high rate low energy expenditure fabrication of solar cells
The objective of this program is to develop high rate, energy efficient solar cell processing techniques based around ion implantation and elimination of all conventional thermal operations. Cells have been fabricated using an abbreviated series of vacuum process operations performed at room temperature.
Kirkpatrick, A. R.↗
Optimum load device for DMOS integrated circuits
Depletion-mode load devices can be integrated with DMOS transistors without any extra diffusions or ion implantation processing steps by judicious choice of the substrate crystal orientation and resistivity. For low voltage operation line-type 1, 1, 1 crystal orientation should be used. The line-type 1, 1, 1 crystal orientation also yields a higher transconductance for the DMOS transistor than the line-type 1, 0, 0 orientation. The geometry of the load device and the DMOS transistor can be made ratioless to conserve area. Self-aligned gates, hitherto considered incompatible with DMOS transistors, have been incorporated in the structure. The experimental DMOS inverters, using a conservative design, have achieved 4-ns propagation delay, 1.3-V operation, and 2-pJ propagation delay-power dissipation product.
Lin, H. C.↗
Silicon solar cells by high-speed low-temperature processing
A new method for silicon solar cell fabrication is being developed around ion implantation and pulsed electron beam techniques. Cells are fabricated totally in a vacuum environment at room temperature. Major reductions result in the time, energy consumption, and waste material generation associated with solar cell production. Cells to date have exhibited air mass zero efficiencies exceeding 10 percent.
Kirkpatrick, A. R.↗
Determination of minority-carrier lifetime and surface recombination velocity with high spacial resolution
Quantitative analysis of the electron beam induced current in conjunction with high-resolution scanning makes it possible to evaluate the minority-carrier lifetime three dimensionally in the bulk and the surface recombination velocity two dimensionally, with a high spacial resolution. The analysis is based on the concept of the effective excitation strength of the carriers which takes into consideration all possible recombination sources. Two-dimensional mapping of the surface recombination velocity of phosphorus-diffused silicon diodes is presented as well as a three-dimensional mapping of the changes in the minority-carrier lifetime in ion-implanted silicon.
Watanabe, M.↗
Low energy production processes in manufacturing of silicon solar cells
Ion implantation and pulsed energy techniques are being combined for fabrication of silicon solar cells totally under vacuum and at room temperature. Simplified sequences allow very short processing times with small process energy consumption. Economic projections for fully automated production are excellent.
Kirkpatrick, A. R.↗
Summary of the NASA space photovoltaic research and technology program
Low cost solar cells and arrays with high end-of-life efficiency are evaluated through two approaches: one, to obtain increased device efficiency at no increase in cost and two, to reduce the manufacturing costs of space solar cells and arrays. Technology efforts encompass high efficiency epitaxial cells, high efficiency wraparound contact solar cells, economical diffusion sources, automated cell fabrication and development of easily applied, durable cover glasses. The examination of ion-implanted profile tailored junctions and additional development of screen printed contact technology to cell development are also considered.
Brandhorst, H. W., Jr.↗
Surface recombination velocity and diffusion length of minority carriers in heavily doped silicon layers
Quantitative analysis of the electron beam-induced current and the dependence of the effective diffusion length of the minority carriers on the penetration depth of the electron beam were employed for the analysis of the carrier recombination characteristics in heavily doped silicon layers. The analysis is based on the concept of the effective excitation strength of the carriers which takes into consideration all possible recombination sources. Two dimensional mapping of the surface recombination velocity of P-diffused Si layers will be presented together with a three dimensional mapping of minority carrier lifetime in ion implanted Si. Layers heavily doped with As exhibit improved recombination characteristics as compared to those of the layers doped with P.
Gatos, H. C.↗
Design and fabrication of solar cell modules
A program conducted for design, fabrication and evaluation of twelve silicon solar cell modules is described. The purpose of the program was to develop a module design consistent with the requirements and objectives of JPL specification and to also incorporate elements of new technologies under development to meet LSSA Project goals. Module development emphasized preparation of a technically and economically competitive design based upon utilization of ion implanted solar cells and a glass encapsulation system. The modules fabricated, tested and delivered were of nominal 2 X 2 foot dimensions and 20 watt minimum rating. Basic design, design rationale, performance and results of environmental testing are described.
Shaughnessy, T. P.↗
A complementary DMOS-VMOS IC structure
A new complementary MOS structure has been fabricated consisting of a p-channel DMOS transistor and an n-channel double-diffused VMOS transistor. The transconductance of each transistor was between 0.85-0.98 of the theoretical transconductance. The threshold voltages have been adjusted by either ion implantation or by adjusting the diffusion profiles. The inverter operation is similar to that of standard CMOS.
Jhabvala, M.↗