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Journal Articles

Low energy proton-induced defects on n$$^{+}$$/p InGaP solar cell

Dharmarasu, N.*; Yamaguchi, Masafumi*; Khan, A.*; Takamoto, Tatsuya*; Oshima, Takeshi; Ito, Hisayoshi; Imaizumi, Mitsuru*; Matsuda, Sumio*

Solar Energy Materials and Solar Cells, 75(1-2), p.327 - 333, 2003/01

 Times Cited Count:3 Percentile:30.75(Energy & Fuels)

n$$^{+}$$/p InGaP junctions were irradiated with 100keV-protons, and the effect on their electrical properties were studied using C-V and DLTS methods.The n$$^{+}$$/p InGaP junctions were fabricated by MOCVD method.They were irradiated up to 1E12 /cm$$^{2}$$ at RT. The carrier removal rate was estimated to be 6.1E4 cm$$^{-1}$$ from the fluence dependence of carrier concentration. H1 peaks which were observed at 400 K in DLTS measurements were found after irradiation.It was concluded that H1 peaks relates residual defects which act as carrier removal centers.

Journal Articles

Majority- and minority-carrier deep level traps in proton-irradiated $$n^{+}/p$$-InGaP space solar cells

Dharmarasu, N.*; Yamaguchi, Masafumi*; Bourgoin, J. C.*; Takamoto, Tatsuya*; Oshima, Takeshi; Ito, Hisayoshi; Imaizumi, Mitsuru*; Matsuda, Sumio*

Applied Physics Letters, 81(1), p.64 - 66, 2002/07

 Times Cited Count:14 Percentile:51.69(Physics, Applied)

We studied the properties of observed defects in n$$^{+}$$/p-InGaP solar cells created by irradiation of protons with different energies.Three majority (hole) and a minority-carrier traps, labeled respectively as HP1 (E$$_{V}$$+0.90$$pm$$0.05eV), HP2 (E$$_{V}$$+0.73$$pm$$0.05eV), H2 (E$$_{V}$$ +0.55eV),and EP1 (E$$_{C}$$ 0.54eV),were identified using deep level transient spectroscopy. All majority-carrier traps were found to act as recombination centers. While the H2 traps present in the proton-irradiated p-InGaP was found to anneal out by minority-carrier injection, the other traps were not.

Journal Articles

Effects of proton irradiation on $$n^{+}p$$ InGaP solar Cells

Dharmarasu, N.*; Khan, A.*; Yamaguchi, Masafumi*; Takamoto, Tatsuya*; Oshima, Takeshi; Ito, Hisayoshi; Imaizumi, Mitsuru*; Matsuda, Sumio*

Journal of Applied Physics, 91(5), p.3306 - 3311, 2002/03

 Times Cited Count:23 Percentile:66.06(Physics, Applied)

3MeV proton irradiation effects on InGaP single junction and InGaP/GaAs two junction cells were studied. The degradation of electrocal properties for InGaP cells was smaller than that for InGaP/GaAs cells. The results of the measurement of spectral response showed the large degradation in long wavelength. This indicates that GaAs cell degrades. The Damage coefficient of minority carrier diffusion length was estimated to be 7.9$$times$$10$$^{-5}$$ for InGaP and 1.6$$times$$10$$^{-4}$$ for GaAs. These values of the damage coefficient for InGaP and GaAs are 580 times and 280 times larger than those for InGaP and GaAs irradiated with 1MeV electrons.

Journal Articles

Deep-level transient spectroscopy analysis of proton-irradiated n$$^{+}$$/p InGaP solar cell

Dharmarasu, N.*; Yamaguchi, Masafumi*; Khan, K.*; Takamoto, Tatsuya*; Oshima, Takeshi; Ito, Hisayoshi; Imaizumi, Mitsuru*; Matsuda, Sumio*

Physica B; Condensed Matter, 308-310, p.1181 - 1184, 2001/12

 Times Cited Count:6 Percentile:38.48(Physics, Condensed Matter)

Carrier concentration and defects in n+/p InGaP irradiated with 100keV-protons (1E10, 5E12 /cm2) were studied.As a result of C-V measurements, the carrier removal rate was estimated to be 6.1E4 /cm2 which was extremely high as compared to 1MeV-electron irradiation case (0.93 /cm). H1 peak whose energy corresponds to Ev+0.90V was obtained from DLTS measurements. This suggests that carrier removal rate in proton-irradiated ones is much higher than that in electron-irradiated ones due to the generation of the defects (H1 peak) which act as majority carrier traps.

Journal Articles

High-radiation-resistant InGaP, InGaAsP, and InGaAs solar cells for multijunction solar cells

Dharmarasu, N.*; Yamaguchi, Masafumi*; Khan, A.*; Yamada, Takashi*; Tanabe, Tatsuya*; Takagishi, Shigenori*; Takamoto, Tatsuya*; Oshima, Takeshi; Ito, Hisayoshi; Imaizumi, Mitsuru*; et al.

Applied Physics Letters, 79(15), p.2399 - 2401, 2001/10

 Times Cited Count:69 Percentile:90.63(Physics, Applied)

The radiation response of 3MeV proton-irradiated InGaP, InGaAsP, and InGaAs solar cells was measured and analyzed in comparison with those of InP and GaAs. The degradation of the minority-carrier diffusion length was estimated from the spectral response. The damage coefficient K$$_{L}$$ for 3MeV proton-irradiated InGaP, InGaAsP and InGaAs was also determined. The radiation resistance increases with increase in the function of In-P bonds in those materials. Minority-carrier injection under forward bias is found to cause partial recovery of the degradation on irradiated InGaP and InGaAsP cells.

Journal Articles

Role of the impurities in production rates of radiation-induced defects in silicon materials and solar cells

Khan, A.*; Yamaguchi, Masafumi*; Oshita, Yoshio*; Dharmarasu, N.*; Araki, Kenji*; Abe, Takao*; Ito, Hisayoshi; Oshima, Takeshi; Imaizumi, Mitsuru*; Matsuda, Sumio*

Journal of Applied Physics, 90(3), p.1170 - 1178, 2001/08

 Times Cited Count:50 Percentile:85.51(Physics, Applied)

1MeV-electron and 10MeV-proton irradiations into Si doped various impurities such as B, Ga, O and C were performed and residual defects in the Si were studied using DLTS and C-V measurements.It was revealed that Ci-Oi whose level is Ev-0.36 eV and Bi-Oi whose energy is Ec-0.18eV were generated. In Ga-doped Si, the generation of Ci-Oi was suppressed. Since Ci-Oi acts as scattering center, this result indicates that the radiation resistance of solar cells is improved by using Ga-doped Si substrates.Furthermore, a new defect level (Ev+18eV) was observed in Ga-dpoed Si by irradiation. This defect level was annealed out above 350 C.

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