INSTABILITIES IN ELECTROLUMINESCENT POROUS SILICON DIODES

The stability of high quantum efficiency, porous silicon (PS) electrol uminescent (EL) diodes have been analyzed under pulsed operation. The results show that EL exhausting is due to a charging of the PS network which recovery is thermally activated (E(r) similar to 0.4 eV). This suggests charge trapping mechanism at larger crystallites with low ban dgap, inhibiting further injection of carriers. Also, forward current is found to be thermally activated, however, with a distinctly lower a ctivation energy (E(j) similar to 0.1-0.2 eV), possibly related to jum ping of carriers over barriers between nearby crystallites. Finally, h igh current densities may lead to thermal runaway causing permanent da mage to the structure. (C) 1996 American Institute of Physics.