PHOTOLUMINESCENCE STUDIES OF ERBIUM-DOPED GAAS UNDER HYDROSTATIC-PRESSURE

The photoluminescence properties of metal-organic chemical vapor depos ition GaAs:Er were investigated as a function of temperature and appli ed hydrostatic pressure. The I-4(13/2)-->(I15/2Er3+)-I-4 emission ener gy was largely independent of pressures up to 56 kbar and temperatures between 12 and 300 K. Furthermore, no significant change in the low t emperature emission intensity was observed at pressures up to and beyo nd the Gamma-X crossover at similar to 41 kbar. In contrast, AlxGa1-xA s:Er alloying studies have shown a strong increase in intensity near t he Gamma-X crossover at x similar to 0.4. These results suggest that t he enhancement is most likely due to a chemical effect related to the presence of Al, such as residual oxygen incorporation, rather than a b and structure effect related to the indirect band gap or larger band g ap energy. Modelling the temperature dependence of the 1.54 mu m Er3emission intensity and lifetime at ambient pressure suggested two domi nant quenching mechanisms. At temperatures below approximately 150 K, thermal quenching is dominated by a similar to 13 meV activation energ y process which prevents Er3+ excitation, reducing the intensity, but does not affect the Er3+ ion once it is excited, leaving the lifetime unchanged. At higher temperatures, thermal quenching is governed by a similar to 115 meV activation energy process which deactivates the exc ited Er3+ ion, quenching both the intensity and lifetime. At 42 kbar, the low activation energy process was largely unaffected, whereas the higher activation energy process was significantly reduced. These proc esses are proposed to be thermal dissociation of the Er-bound exciton, and energy back transfer, respectively. A model is presented in which the Er-related electron trap shifts up in energy at higher pressure, increasing the activation energy to back transfer, but not affecting t hermal dissociation of the bound exciton through hole emission. (C) 19 97 American Institute of Physics.