THE ELECTRICAL-PROPERTIES OF POROUS SILICON PRODUCED FROM N(+) SILICON SUBSTRATES

Current transport through porous silicon (PS) films of 50% porosity fa bricated from n-type (0.018 Omega cm) substrates has been studied. Thi s has been achieved by comparing the current density J vs, voltage V c haracteristics for metal/PS/n(+)-Si/aluminium and metal/PS/aluminium d evices. For the case of metal = aluminium, the J-V characteristics are ohmic. For metal = gold, the J-V characteristics are consistent with the formation of a rectifying Schottky barrier of height 0.74 eV at th e Au/PS contact. As the Au/PS contact is forward biased for positive b ias on the gold, this implies that the PS is n type in nature. This is confirmed by Hall effect measurements which give a carrier concentrat ion and Hall mobility of 1.3 x 10(13) cm(-3) and 30 cm(2) V-1 s(-1) re spectively. This carrier concentration is consistent with the pinning of the Fermi level at an energy which is approximately the same as tha t of the (-/O) level of P-b centres at an SiO2-Si interface.