Stable aluminium ohmic contact to surface modified porous silicon

A stable low resistance aluminium (Al) contact to porous silicon (PS) could be achieved by chemically modifying PS surface with palladium chloride (PdCl2) solution. Palladium (Pd) was dispersed over the PS surface by chemical dipping method using very low concentration of PdCl2 solution (0.01 M) and for a very short duration of time (5 s). Field emission scanning electron microscopy (FESEM) was performed to investigate the morphology of the modified PS surface. Digital X-ray image mapping and energy dispersive X-ray (EDAX) spectras were taken to confirm the dispersion and formation of Pd clusters on the porous silicon surface. X-ray photoemission spectroscopy (XPS) confirms that the presence of oxygen is higher in Pd modified porous silicon than that of unmodified one. Aluminium (Al) was thermally evaporated on Pd modified surfaces and the study of J–V characteristics showed a linear relationship. Therefore the specific contact resistance (ρc) could be measured by transmission line model (TLM) method. Stability of the contact was studied for a time period of around 30 days and no significant ageing effect could be observed.