Numerical Analysis Of Carriers’ Transport Mechanism Of GaInP/GaAs/Ge Space Solar Cells

In this paper, the basic laws of electrical parameters degradation of GaInP/GaAs/Ge solar cells are gotten under different energy electrons irradiation by ground simulation test irradiation. The carriers’ transport mechanism in cells is analyzed using PC1 D simulation program. The change of carriers’ concentration and the minority carriers’ diffusion length with the irradiation particle fluency is established in GaInP/GaAs/Ge under different energy particle irradiation. The damage coefficients of minority carriers’ diffusion length and majority carriers’ removal rate of GaInP/GaAs/Ge solar cells are estimated. The micro damage mechanism of GaInP/GaAs/Ge solar cells is revealed base on the fitting process of PC1 D.The results show that electron irradiation mainly is caused by GaAs middle cell damage. The degradation amplitude of the electrical parameter of GaInP/GaAs/Ge solar cells increases with increasing of irradiation electron energy. The majority carriers’ removal rate and minority carriers’ diffusion length damage coefficient increase with increasing of electrons energy.Proton irradiation mainly is caused by GaAs sub cell damage. The majority carriers’ removal rate and minority carriers’ diffusion length damage coefficient decrease with increasing of protons energy. The degradation amplitude of GaInP/GaAs/Ge solar cells electrical parameter decreases with the increasing of proton energy. SRIM simulation results show that the vacancy concentration decreases with increasing of proton energy in GaAs sub cell.Radiation damage mechanism of low energy proton is different with high energy proton. GaInP top cell carriers’ removal rates are 2.15?103 cm-1, 1.24?104 cm-1, 1.16?104 cm-1, 1.05?104 cm-1 and minority carriers’ diffusion length damage coefficient are 8.8?10-4, 7?10-4, 1.45?10-3, 2.12?10-3 by fitting GaInP/GaAs/Ge solar cell spectral response under 40 keV, 100 keV, 130 keV, 170 keV protons irradiation. Carrier removal rates of GaAs middle cell is 5.95?104 cm-1, 2.91?104 cm-1 under 130 keV, 170 keV proton irradiation. In GaAs middle cell the damage coefficients of minority carrier diffusion length is 6.20?10-6, 3.68?10-3 under 130 keV, 170 keV proton irradiation. SRIM simulation results show that proton of different energy irradiate GaInP/GaAs/Ge solar cell causes solar cell’s different region being damaged in different degree. 40 keV proton does damage Ga InP top cell in the emitter region. 100 keV proton does damage GaInP top cell in the base region. 130 keV protons cause GaAs sub cell in emitter region and space charge region damage. 170 keV protons cause GaAs sub cell in base region and space charge region damage.The results show that the main reasons of degradation of electrical parameters are the minority carriers’ diffusion length shortening and majority carriers’ removal effect.