ELECTRICAL CHARACTERISTICS OF RECTIFYING POLYCRYSTALLINE SILICON SILICON-CARBIDE HETEROJUNCTIONS

This paper presents a study of the rectifying properties of heavily do ped polycrystalline silicon (polysilicon) on 4H silicon carbide (4H-Si C). Current properties and barrier heights were found using analysis o f the heterojunction. This revealed that Schottky analysis would be va lid for the large barrier height devices. Isotype and an-isotype devic es were fabricated on both p-type and n-type SiC and the electrical ch aracteristics were investigated using capacitance vs voltage measureme nts, current vs voltage measurements (I-V), and temperature I-V measur ements. Extraction of the barrier height, built-in potential, and Rich ardson constant were made and then compared to theoretical values for the heterojunction. Temperature I-V measurements demonstrated that the current transport mechanism is thermionic emission, confirming the va lidity of the Schottky diode model. The I-V characteristics show near ideal diode rectifying behavior and the capacitance-voltage characteri stics show ideal junction space charge modulation for all polysilicon/ SiC combinations. These experimental results match well with heterojun ction band-offset estimated barrier heights and demonstrate that the b arrier height of the polysilicon/4H SiC interface may be controlled by varying the polysilicon doping type.