Abstract

Second-harmonic (SH) generation has been used to probe the effects of a static electric (dc) field on the optical nonlinearities in epitaxial GaN, a wide-band-gap III-V semiconductor. Investigations were performed at SH photon energies near the absorption edge (E_gap = 3.4 eV) with a dc-field amplitude in the GaN sample of the order of 10⁴ to 10⁵ V/cm. Under these conditions, the reflected SH intensity exhibited a significant increase relative to the nonlinear response at the zero-static-field condition at SH photon energies above the band gap. These nonlinear results, coupled with complementary linear electroreflectance data, suggest a χ⁽³⁾ contribution to the nonlinear polarization at 2ω as the primary enhancement mechanism.

© 1995 Optical Society of America