OPTO-ELECTRICAL CHARACTERIZATION OF n+-ZnO/i-ZnO BILAYERS GROWN IN SITU BY REACTIVE EVAPORATION WITHOUT USING EXTRINSIC DOPING

Abstract

This work describes a procedure to grow in situ highly transparent n+-ZnO and i-ZnO thin films sequentially deposited by plasma assisted reactive evaporation without using extrinsic doping. Good reproducibility of the thickness and opto-electrical properties of the films was achieved through a novel electronic control developed using the virtual instrumentation concept. For that, a virtual instrument (VI) was implemented to control the process using PID (proportional integral differential) and PWM (pulse width modulation) as control algorithms. By optimizing the design of the reactor and deposition parameters, n+-ZnO and i-ZnO films with resistivities around 6 x10-4 cm and 104 cm respectively and transmittances greater than 85% (in the visible region) were obtained with this method. From Urbach energy measures we have found that n+-ZnO films deposited controlling the quantity of zinc that arrives to the reactor appropriately, have a low density of structural defects. Results regarding electrical transport properties of the ZnO films, obtained from temperature dependent measurements of both conductivity and mobility, are also reported.

Keywords

• Películas delgadas de ZnO
• evaporación reactiva
• propiedades opto-eléctricas
• instrumentación virtual
• dopaje intrínseco.