Role of Copper in the Degradation of GaAs Electroluminescent Diodes

Bahraman, A.; Oldham, W.G.

doi:10.1063/1.1661507

Cited by 21 publications

(4 citation statements)

References 14 publications

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“…Implicitly contained in this reasoning is the assumption that Cu is not present on the cell prior to test. The detrimental effect of Cu on the performance of III‐V devices is well known in semiconductor manufacturing . Therefore, significant effort is undertaken there to avoid Cu contamination.…”

Section: Discussionmentioning

confidence: 99%

A mechanism of solar cell degradation in high intensity, high temperature space missions

Zimmermann¹,

Nomayr²,

Kolb³

et al. 2011

Progress in Photovoltaics

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The behavior of standard space photovoltaic assemblies in a high intensity, high temperature environment (HIHT) is addressed. Experimentally, an HIHT environment, typical for missions to the inner planets of the solar system such as Mercury, characterized by temperatures of 500K and 11 solar constant irradiance in the ultraviolet region below 400 nm, was simulated in a vacuum. Independently of the triple junction cell technology used, module degradation up to 20% in power was observed during several hundred hours of test. Electroluminescence analysis identified discrete top cell shunts close to the cell edge, in particular around the frontside contact pads. Cross‐sectional transmission electron microscopy performed on several degraded cells revealed an etched contact pad metallization/cap layer interface and more importantly, several 100‐nm large, oriented Cu3P inclusions at the shunted locations. A chemical degradation mechanism is proposed. Short wavelength ultraviolet light interacting with polysiloxanes used as module encapsulant produces hydrogen and methyl radicals. With these building blocks, an organic acid can be formed on external reaction surfaces such as the Ag busbars that simultaneously serve as a source of oxygen. Cu traces present in the Ag segregate to the surface and are transported by this acid to the contact pad of the cell in the liquid phase. An adapted cell design was developed to prevent this degradation mechanism believed to be of relevance for all HIHT space environments. A several hundred micrometer‐wide rim composed of the outermost cell area is electrically separated from the inner cell area and provides a barrier against environmental attack. None of the photovoltaic assemblies featuring this mesa cell design showed any fill factor‐induced power degradation any more. Copyright © 2011 John Wiley & Sons, Ltd.

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Section: Discussionmentioning

confidence: 99%

A mechanism of solar cell degradation in high intensity, high temperature space missions

Zimmermann¹,

Nomayr²,

Kolb³

et al. 2011

Progress in Photovoltaics

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“…In LPE GaAs grown from Cu-doped melts, only the 0.14 and 0.44 eV levels are observed (41). Degradation of GaAs light emitting diodes has been associated with Cu contamination of the p-GaAs side of the junction (42). In GaP acceptor levels at Ev + 0.17, 0.64, and 0.82 eV have been reported (43)(44)(45) but Cu levels in GaAs0.6Po.4 appear not to have been studied.…”

Section: Results Of the Metal Diffusion Studiesmentioning

confidence: 99%

Hole Diffusion Lengths in VPE GaAs and GaAs0.6 P 0.4 Treated with Transition Metals

Partin

Milnes

Vassamillet

1979

J. Electrochem. Soc.

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The effects of several metals on L, in GaAs and GaAs0.6Po.4 have been evaluated. Diffusion of Co at 700~ for 5 rain into VPE n-GaAs0.6Po.4 is found to produce a considerable reduction of Lp. Lesser degradation is caused by Ni, whereas Cu, Cd, and Zn improve L,. In VPE n-GaAs, diffusions of Co, Cu, W, and Cd improve Lp. These improvements are believed to be caused by gettering of lifetime killing deep impurities, such as Co and Ni, by shallow diffused junctions. The metals that degrade LD appear to be ones with small tetrahedral covalent radii.

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“…Although these results do not prove that copper was the cause of degradation, they show that reduction of either contamination or the number of point defects increased the LED life. Bahraman and Oldham (1972) similarly found that copper contamination of gallium arsenide LEDS significantly increased the degradation rates of their devices.…”

Section: Light-emitting Diodes (Low-current-density Devices)mentioning

confidence: 90%

The degradation of semiconductor light-emitting diodes, high-radiance lamps and lasers

Ohara¹

1977

J. Phys. D: Appl. Phys.

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Detailed experimental results and suggested theories on the degradation of light-emitting diodes (LEDS), high-radiance lamps and semiconductor lasers are reviewed. Experimental results on LEDS show that a number of light-degrading mechanisms can operate which probably include migration of impurities or point defects. Dislocations when present in high densities also give rise to degradation in LEDS. Extrapolated lives to half intensity of between lo5 and lo7 h have been commonly projected for these devices, and this rather slow rate of degradation appears to have been achieved by minimizing impurity contamination, reducing strain and minimizing the dislocation density in the carrier recombination region.Relatively long lives have also been predicted for high-radiance, high-currentdensity lamps from thermally accelerated life-tests. Dark-spot and dark-line defects have been observed in these lamps, and samples which develop this structure have to be rejected at early stages of testing in order that long lives can be guaranteed. In one case, the dark structure has been shown to result from the formation of tangles of dislocations generated during fabrication. High-current-density lamps which are free from dark structure also have projected lives of between 105 and 107 h.Generally, laser diodes can now be made which have lives in excess of lO4h. As with high radiance lamps, however, if dislocations are present in the active region, then the useful life of the device is reduced to hundreds of hours or less. Considerable care must therefore be exercised in the fabrication and in layer growth procedures to prevent the introduction of dislocations in the active region. Details of the dark structure resulting from dislocations is reviewed and consideration is given to the remaining causes of degradation in lasers.

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Role of Copper in the Degradation of GaAs Electroluminescent Diodes

Cited by 21 publications

References 14 publications

A mechanism of solar cell degradation in high intensity, high temperature space missions

A mechanism of solar cell degradation in high intensity, high temperature space missions

Hole Diffusion Lengths in VPE GaAs and GaAs0.6 P 0.4 Treated with Transition Metals

The degradation of semiconductor light-emitting diodes, high-radiance lamps and lasers

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