I-V and C-V characterization of semiconductor thin flms

Abstract

Cuprous oxide (CU20) and ZnSe thin films were potentiostatically electrodeposited on indium-doped tin oxide (ITO) substrates in order to investigate the I-V and C-V characteristics of ITO/n-Cu20/(p-CuxS or metal or electrolyte) and ITO/p-ZnSe/electrolyte systems, An electrochemical cell containing aqueous solutions of 0-1 M sodium acetate and 1.6x10-2 M cupric acetate was used for electro deposition of CU20 thin films on ITO-coated glass substrates. Potentiostatic condition of -250 mV against standard calomel electrodes (SEC) was used for the electro deposition, To convert the top layers of the CU20 to Cu.S by sulphidation, exposed the surface to a spray of aqueous solution of sodium sulphide or to a mixture of hydrogen sulphide and nitrogen gases to foam ITO/n-Cu20/p-CuxS system. For the system ITO/n-Cu2O/metal, metal layer was evaporated on to the n-Cu20 surface. An electrolyte of 0.1 M sodium acetate was used in the ITO/n-Cu20/electrolyte system. Electro deposition of ZnSe thin films were carried out under potentionstatic condition at -550 mV against SCE using aqueous solutions of 0.1 M ZnS04 and 10-5 M Se02 at the temperature of 65� C. The theoretical and experimental 1-V characteristics of ITO/n-Cu2O/(P-CuxS or metal or electrolyte) system suggest that CU20 films made on ITO substrate form Schottky type junctions at the back contact in addition to the CU20/(p-CuxS or metal of electrolyte) junctions. Furthermore, C-V characteristics suggest that the doping concentration of the CU20 layer is in the order of 10 18. Light and dark I-V measurements of doped and undoped lTO/ZnSe in KI electrolyte suggest the p-type photoconductivity in this system and C-V measurements confirmed it.