DIELECTRIC-PROPERTIES OF AMORPHOUS ALUMINUM PHOSPHATE THIN-FILMS

Thin insulating layers on III-V semiconductors of aluminium phosphate have been obtained by the 'pyrosol' process. The electrical properties of these deposits were determined from direct and alternating current (dc and ac) measurements. Their conductivity under direct current is weak (sigma(dc), almost-equal-to 10(-10)-10(-11) (OMEGA cm)-1) but higher than that of AlPO4 bulk crystallized material (sigma(dc) almost-equal-to 10(-22) (OMEGA cm)- 1). The ac experiments allowed improvement of the understanding of the conduction phenomena in accordance with the correlated barrier hopping (CBH) model established for amorphous chalcogenides and silica. The sites involved in the conduction processes are structural defects related directly to the oxygen excess present in these thin films which lead to the formation of M-O dangling bonds (M = Al or P).