p⁺−n⁻−n⁺-type power diode with crystalline/nanocrystalline Si mosaic electrodes^*

Using p⁺-type crystalline Si with n⁺-type nanocrystalline Si (nc-Si) and n⁺-type crystalline Si with p⁺-type nc-Si mosaic structures as electrodes, a type of power diode was prepared with epitaxial technique and plasma-enhanced chemical vapor deposition (PECVD) method. Firstly, the basic p⁺−n⁻−n⁺-type Si diode was fabricated by epitaxially growing p⁺- and n⁺-type layers on two sides of a lightly doped n⁻-type Si wafer respectively. Secondly, heavily phosphorus-doped Si film was deposited with PECVD on the lithography mask etched p⁺-type Si side of the basic device to form a component with mosaic anode. Thirdly, heavily boron-doped Si film was deposited on the etched n⁺-type Si side of the second device to form a diode with mosaic anode and mosaic cathode. The images of high resolution transmission electronic microscope and patterns of X-ray diffraction reveal nanocrystallization in the phosphorus- and boron-deposited films. Electrical measurements such as capacitance–voltage relation, current-voltage feature and reverse recovery waveform were carried out to clarify the performance of prepared devices. The important roles of (n⁻)Si/(p⁺)nc-Si and (n⁻)Si/(n⁺)nc-Si junctions in the static and dynamic conduction processes in operating diodes were investigated. The performance of mosaic devices was compared to that of a basic one.