Ph.D Thesis

Ph.D StudentEl-Bahar Aron
SubjectContacts and Passivations for Porous Silicon
DepartmentDepartment of Electrical and Computer Engineering
Supervisor PROFESSOR EMERITUS Yael Nemirovsky


Porous silicon is a promising material for the upcoming light emitting diode technologies. Three major drawbacks slow this technology becoming the leading technology: low conductivity, bad solid state contacts and rapid aging of this layer.

For the poor electrical conductivity we exhibit the solutions: using heavily doped silicon substrates and the gas phosphor doping preprocess applied to the porous silicon layer. For the solid state electrical contacts the techniques exhibited in this work are metal deposition and annealing, sputtering of transparent conducting materials and conducting organic materials. The sputtered transparent conducting material got better surface coverage, but creates a rectifying contact. The conductive organic materials creating high efficient contacts and got good penetration to the whole porous silicon surface and form an ohmic contact to p-type porous silicon and rectifying contact to n-type porous silicon. For the stabilization of the porous silicon layer we exhibit two unique approaches including the exposure of the porous layer to highly active gas (NF3) and the usage of ultrasound energy to avoid later oxidation.

In this work we fabricated porous silicon layers using dry and wet electrochemical processes on both n-type and p-type silicon substrates. The electro-optical devices that were formed and investigated are planar wave-guides, mirrors, micro-cavities and wave-guide couplers. The electrical devices that were fabricated are: porous silicon p-type and n-type junction, Shotkky and ohmic contacts to the porous silicon, heterojunctions with porous silicon, detectors and light emitting diodes.