PHOTOLUMINESCENCE EXCITATION MEASUREMENTS ON ERBIUM IMPLANTED GAN

The temperature dependence of the optical excitation cross section of Er implanted n-type GaN was studied using photoluminescence excitation spectroscopy, Due to the large 3.4 eV band gap of GaN, it was possibl e to probe two Er absorption lines using a tunable Ti:sapphire laser i n the 770-1010 nm range, Photoluminescence excitation spectra exhibiti ng several Stark splittings revealed a complex dependence upon tempera ture. The largest excitation cross section in the third excited state was 1.65 x 10(-20) cm(2) at an excitation wavelength of 809.4 nm when measured at 77 K. This value is roughly three times larger than the cr oss section in the second excited state at 4.8 x 10(-21) cm(2) when pu mping at 983.0 nm. The Er-related photoluminescence was reduced betwee n 1.5 and 4.8 times when going from 77 K to room temperature, except w hen pumping around 998 nm. At this excitation wavelength the room temp erature photoluminescence was stronger by a factor of 1.26 compared to that at 77 K. (C) 1997 American Institute of Physics.