Nitrogen-activated transitions, level repulsion, and band gap reduction inGaAs1-xNx with x < 0.03

We report electroreflectance spectra for a series of GaAs1-xNx samples with x less than 0.03. For all samples, the fundamental band gap transition (E- 0) and the transition from the spin-orbit split-off valence band (E-0 + Del ta(0)) are observed. For samples with x greater than or equal to 0.008, an additional transition (E+) is observed. With increasing nitrogen content, t he increase in E+ is linear in, and nearly equal to, the band gap reduction indicative of a nitrogen-induced level repulsion. The directly observed E transition may arise from either a nitrogen-related resonant level or a di sorder-activated indirect transition. [S0031-9007(99)08950-4].