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Results for “P-N JUNCTION”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 91 records · Page 5
All sourcesNASA NTRSDOE OSTI
NASA NTRS1976

Fabrication of polycrystalline solar cells on low-cost substrates

A new method of producing p-n junction semiconductors for solar cells was described; the principal objective of this investigation is to reduce production costs significantly by depositing polycrystalline silicon on a relatively cheap substrate such as metallurgical-grade silicon, graphite, or steel. The silicon layer contains appropriate dopants, and the substrates are coated with a diffusion barrier of silica, borosilicate, phosphosilicate, or mixtures of these compounds.

Chu, T. L.↗
NASA NTRS1976

Research and development for improved lead-salt diode lasers

A substantial increase in output power levels for lead-salt diode lasers, through the development of improved fabrication methods, as demonstrated. The goal of 1 mW of CW, single-mode, single-ended power output, was achieved, with exceptional devices exhibiting values greater than 8 mW. It was found that the current tuning rate could be controlled by adjusting the p-n junction depth, allowing the tuning rate to be optimized for particular applications. An unexpected phenomenon was encountered when crystal composition was observed to be significantly altered by annealing at temperatures as low as 600 C; the composition was changed by transport of material through the vapor phase. This effect caused problems in obtaining diode lasers with the desired operating characteristics. It was discovered that the present packaging method introduces gross damaging effects in the laser crystal through pressure applied by the C-bend.

Butler, J. F.↗
NASA NTRS1975

Ion implanted photodiode detectors in epitaxial /Ga/x/In/1-x//As

Ion implanted p-n junction photodiodes in epitaxially grown (Ga(x)In(1-x))As material are reported on here. Photoresponse in these diodes was investigated for approximately the entire composition range of x between zero and one. High values for quantum efficiency were obtained for the devices with a high value of x.

Ajmera, P. K.↗
NASA NTRS1976

Determination of surface recombination velocity in heavily doped silicon

A method was developed and successfully tested for the determination of the effective surface recombination velocity of silicon layers doped by diffusion of phosphorus to a level of 10 to the 19th to 10 to the 21st per cu cm. The effective recombination velocity was obtained from the dependence of the electron-beam-induced current on the penetration of the electron beam of a scanning electron microscope. A special silicon diode was constructed which permitted the collection at the p-n junction of the carriers excited by the electron beam. This diode also permitted the study of the effects of surface preparation on the effective surface recombination velocity.

Watanabe, M.↗
NASA NTRS1977

A computer analysis of heterojunction and graded composition solar cells

The development and application of a variable composition solar cell computer analysis program is discussed. The basic device equations are derived and results of the computer analysis of several Al(x)Ga(1-x)As and GaAs(1-x)P(x) solar cell structures are presented along with a discussion of the effects of interface states and various composition and doping profiles on maximum solar cell efficiency. Interface states are found to be responsible for a severe reduction in the efficiency of GaAs(1-x)P(x) cells, but do not significantly affect the behavior of Al(x)Ga(1-x)As cells. The depth of the p-n junction below the wide bandgap window layer is a critical factor in determining the loss of minority carriers to interface recombination at the heterojunction.

Sutherland, J. E.↗
NASA NTRS1978

Determination of bulk diffusion lengths for angle-lapped semiconductor material via the scanning electron microscope: A theoretical analysis

A standard procedure for the determination of the minority carrier diffusion length by means of a scanning electron microscope (SEM) consists in scanning across an angle-lapped surface of a P-N junction and measuring the resultant short circuit current I sub sc as a function of beam position. A detailed analysis of the I sub sc originating from this configuration is presented. It is found that, for a point source excitation, the I sub sc depends very simply on x, the variable distance between the surface and the junction edge. The expression for the I sub sc of a planar junction device is well known. If d, the constant distance between the plane of the surface of the semiconductor and the junction edge in the expression for the I of a planar junction is merely replaced by x, the variable distance of the corresponding angle-lapped junction, an expression results which is correct to within a small fraction of a percent as long as the angle between the surfaces, 2 theta sub 1, is smaller than 10 deg.

Vonroos, O.↗
NASA NTRS1978

Nuclear electric power sources

Measurements on radioactive commercial p-n junction silicon cells show that these units are capable of delivering several hundred microwatts per curie of Am-241 alpha source, indicating their usefulness in such electronic devices as hearing aids, heart pacemakers, electronic watches, delay timers and nuclear dosimeter chargers. It is concluded that the Am-241 sources are superior to the beta sources used previously, because of higher alpha specific ionization and simultaneous production of low energy photons which are easily converted into photoelectrons for additional power.

Singh, J. J.↗
NASA NTRS1976

Investigation of the double exponential in the current-voltage characteristics of silicon solar cells

A theoretical analysis is presented of certain peculiarities of the current-voltage characteristics of silicon solar cells, involving high values of the empirical constant A in the diode equation for a p-n junction. An attempt was made in a lab experiment to demonstrate that the saturation current which is associated with the exponential term qV/A2kT of the I-V characteristic, with A2 roughly equal to 2, originates in the space charge region and that it can be increased, as observed on ATS-1 cells, by the introduction of additional defects through low energy proton irradiation. It was shown that the proton irradiation introduces defects into the space charge region which give rise to a recombination current from this region, although the I-V characteristic is, in this case, dominated by an exponential term which has A = 1.

Wolf, M.↗
NASA NTRS1977

LPE growth of GaAs-Ga/1-x/Al/x/As solar cells

The procedures for the liquid phase epitaxial (LPE) growth of high efficiency p-Ga(1-x)Al(x)As,p-GaAs,n-GaAs solar cells have been developed. The methods are based on forming the structure by a one-step process in which the Zn-diffused p-n junction in the n-type GaAs substrate forms in conjunction with the LPE growth of the Zn-doped p-Ga(1-x)Al(x)As layer. For structures with 1-10 micron thick Ga(1-x)Al(x)As layers, an isothermal soak of the GaAs substrate in a saturated Ga-Al-As: Zn melt followed by ramp cooling produces good cells. For structures with less than one micron thick Ga(1-x)Al(x)As layers, it is necessary to isothermally soak the GaAs substrate in an undersaturated melt, and ramp cooling is not required.

Woodall, J. M.↗
NASA NTRS1965

GaAs-Si photon-activated switch.

Light activated low level switch consisting of electroluminescent GaAs p-n diode and double emitter silicon transistor

SWITCHING ELEMENT↗