Photoluminescence and Bandgap Narrowing in Heavily Doped n-GaAs

Extremely heavily doped n-GaAs was produced by pulsed-laser annealing of Si implanted GaAs, achieving carrier concentrations exceeding 3.2×1019/cm3. Our photoluminescence (PL) spectra indicate a bandgap narrowing due to heavy n-type doping with a functional form of Δεg(eV) = - 6.3 × 10cm-8[(cm-2)]1/3 . At the highest carrier concentration, the bandgap shrinkage reaches -200 meV and the electron Fermi energy is -410 meV. These large values indicate that there exists a considerable conduction band “stretch” between the Γ and L-valley of GaAs for very high n-type concentrations.