| 초록 |
Epitaxial growth of III-V compound semiconductor on Si has long been researched since Si is the prevalent platform for microelectronics while III-V can be used for optoelectronics due to its direct bandgap and versatile heterojunctions. In this talk, I will introduce non-catalytic growth of high-quality InxGa1-xAs (x = 0.2–1) nanowires on Si as a feasible means of integrating III-V semiconductor on Si. InxGa1-xAs NWs were grown using metalorganic chemical vapor deposition (MOCVD) without catalysts or masks. The epitaxial growth is initiated via Volmer-Weber mechanism, resulting in uniform, nontapered, high aspect ratio NW arrays with a density exceeding 1 × 108/cm2. NW diameter ( 30–250 nm) is inversely proportional to the lattice mismatch between InxGa1-xAs and Si ( 4–11%), and can be further tuned by MOCVD growth condition. Indium rich NWs show more zinc-blende and Ga-rich NWs exhibit dominantly wurtzite polytype, as confirmed by scanning transmission electron microscopy (STEM) and photoluminescence spectra. Solar cells fabricated using an n-type In0.3Ga0.7As NW array on a p-type Si(111) substrate with a 2.2% area coverage, operates at an open circuit voltage, Voc, and a short circuit current density, Jsc, of 0.37 V and 12.9 mA/cm2, respectively. This work represents the first systematic report on direct 1D heteroepitaxy of ternary InxGa1-xAs NWs on silicon substrate in a wide composition/bandgap range that can be used for wafer-scale monolithic heterogeneous integration for high performance photovoltaics. |
