Electrically pumped wavelength-tunable ultraviolet random lasing from Mg_xZn_1-xO films on Si

We report the electrically pumped wavelength-tunable ultraviolet random lasing from Mg(x)Zn(1-x)O films with different bandgap energies, which act as the semiconductor components in metal-insulator- semiconductor (MIS) structures fabricated on Si substrates. When the metal (Au herein) gates of the MIS structures are applied with sufficiently high positive voltages, random lasing from the Mg(x)Zn(1-x)O films occurs, featuring a series of narrow spikes in the emitted spectra. Overall, the central wavelength of the random lasing spectrum is tuned from approximately 377 to 352 nm with the increase of x value in Mg(x)Zn(1-x)O from 0 to 0.35. The mechanism for the electrically pumped random lasing has been tentatively elucidated taking into account both the multiple optical scattering and the optical gain proceeding in the Mg(x)Zn(1-x)O films.