Rare-Earth Doped Gallium Nitride (GaN)- An Innovative Path Toward Area-scalable Solid-state High Energy Lasers Without Thermal Distortion
Final rept Dec 2007-Dec 2008
ARMY RESEARCH LAB ADELPHI MD SENSORS AND ELECTRON DEVICES DIRECTORATE
Pagination or Media Count:
We have demonstrated, for the first time, in situ neodymium Nd doping of gallium nitride GaN by plasma-assisted molecular beam epitaxy PA-MBE. The Nd doping is controlled by the GaN growth conditions and the Nd effusion cell temperature. The Rutherford backscattering spectroscopy RBS and secondary ion mass spectrometry SIMS data indicated Nd doping as high as 8 at. , with no evidence of phase segregation identified by x-ray diffraction XRD for Nd up to 1 at. . The Nd incorporation reached a limit while maintaining crystal quality. Strong room-temperature RT luminescence corresponded to the three characteristic Nd emission multiplets, with the Stark energy levels resolved by photoluminescence PL and photoluminescence excitation PLE. Although the 4f electrons were well shielded from the host material, we were still able to observe weak electron-phonon interactions. Spectral correlation of the multiplets for above 325 nm and below 836 nm GaN bandgap excitation implied enhanced substitutional doping at the Ga site. The highest RT PL intensities corresponded to a doping level between 0.11 at. . The enhanced substitutional doping at the Ga site and low optical loss in waveguide structures suggests GaNNd with a high enough Nd concentration has significant potential for use in simple, area-scalable, RT, diode-pumped, solid-state high energy lasers HELs.
- Lasers and Masers