Room temperature excitonic stimulated emission from zinc oxide epilayers grown by plasma-assisted MBE

Spontaneous, stimulated and laser emission spectra of ZnO epitaxial layers, grown by plasma-assisted molecular beam epitaxy, are presented. Samples are found to exhibit high-intensity near band-edge emissions at room temperature, this is attributed to a dramatic reduction in the intensity of the deep-level emission which dominates ZnO produced by other techniques. Stimulated emission at room temperature is found to be due to exciton-exciton scattering at intermediate excitation intensities while at higher excitation intensities electron-hole plasma emission dominates. An example of longitudinal cavity modes is provided, clearly showing lasing at room temperature.