Photoexcited carrier trapping and recombination at Fe centers in GaN

Fe doped GaN was studied by time-resolved photoluminescence (PL) spectroscopy. The shape of PL transients at different temperatures and excitation powers allowed discrimination between electron and hole capture to Fe3+ and Fe2+ centers, respectively. Analysis of the internal structure of Fe ions and intra-ion relaxation rates suggests that for high repetition rates of photoexciting laser pulses the electron and hole trapping takes place in the excited state rather than the ground state of Fe ions. Hence, the estimated electron and hole capture coefficients of 5.5 x 10(-8) cm(3)/s and 1.8 x 10(-8) cm(3)/s should be attributed to excited Fe3+ and Fe2+ states. The difference in electron capture rates determined for high (MHz) and low (Hz) (Fang et al., Appl. Phys. Lett. 107, 051901 (2015)) pulse repetition rates may be assigned to the different Fe states participating in the carrier capture. A weak temperature dependence of the electron trapping rate shows that the potential barrier for the multiphonon electron capture is small. A spectral feature observed at similar to 420 nm is assigned to the radiative recombination of an electron in the ground Fe2+ state and a bound hole. Published by AIP Publishing.