RADIATION STUDY OF GAAS SOLAR CELLS GROWN ON GE/SIXGE1-X/SI SUBSTRATES

摘要

Proton radiation studies of promising GaAs/Si devices and solar cells using SiGe interlayers are described. 2MeV proton radiation at various doses was applied to both p+n and n+p configured GaAs devices grown on low dislocation density SiGe/Si substrates. To provide a systematic evaluation of both, grown-in and radiation induced deep levels, identical devices were grown on GaAs and Ge substrates and subjected to the same radiation conditions. High quality as-grown GaAs material on SiGe/Si was confirmed by Deep Level Transient Spectroscopy (DLTS) studies showing trap densities that closely match for all substrates, with concentrations at or below 5*1013 cm-3 for both n and p type GaAs. DLTS experiments revealed that identical radiation induced traps are generated regardless of substrate. Introduction rate studies show either similar or lower trap incorporation rate for devices on SiGe/Si compared to Ge and GaAs substrates suggesting a different defect introduction mechanism linked with the unique properties of the SiGe/Si substrate. A possible explanation may be the absorption of radiation induced point defects by the dislocation network present in the SiGe/Si substrate. Solar cell results demonstrate that the SiGe/Si buffer approach to achieve III-V/Si solar cell integration is robust for space applications requiring radiation resistance.