Preparation Of Semiconductor Boron Nitride Thin Films And Research On The Characteristics Of Their Heterojunction

Cubic boron nitride (cBN) thin films have significant and potential technological application prospect in cutting tools, electronic and optical devices, etc., because cBN possesses excellent physical and chemical properties, such as ultrahigh hardness only inferior to diamond, inertness against oxidation at high temperature, uneasy reaction with iron group metal, as well as the possibility of using as n-and p-type doped semiconductors. The preparation and property research of cBN film have been one of difficult and attractive field in the scientific world. This dissertation focuses on the preparation of high quality cBN films and the characteristics of BN(n-type)/Si(p-type) heterojunction.Boron nitride (BN) thin films were deposited on Si substrates using the conventional radio-frequency (RF) sputtering system, with hexagonal boron nitride (hBN) target and working gas of mixture of nitrogen and argon. The influence of various factors, such as substrate bias voltage and temperature, resistivity of Si wafer, etc., on the preparation of cBN has been studied systematically. The films were characterized by Fourier transform infrared spectrophotometer (FTIR) and X-ray photoelectron spectroscopy (XPS). Moreover, the surface morphology of the films was observed by Atomic Force Microscopy (AFM) and Scanning Electron Microscope (SEM). In addition, the thickness of films was measured by Alpha-step Meter. On the p-type Si wafer, the n-type BN film was prepared by implanting sulfur ions into it. I-V curves of BN (n-type)/Si (p-type) heteroj unction were obtained by the low Resistance Meter.Based on the optimized deposition conditions, we advanced a two-step approach, in which the deposition process was divided into two steps. Either the substrate temperature or the bias voltage as a parameter of particular interest was reduced in the second step. By this means, the cBN film with cubic phase content up to 100% was prepared. The results from Fourier infrared spectra showed that, the stress in the film deposited by the two-step approach is less than that in the film using conventional method by approximate 4.7GPa. Additionally, a relatively higher substrate resistivityfavored the cBN formation and compressive stress. AFM image showed that the film grows in the form of column. The film in the atmosphere did not peel off after six months.Resistivity of the doped films decreased by six order of magnitude. The current-voltage (I-V) characteristics showed significant rectifying behavior, breakdown voltage of 1.1 V and threshold voltage of 4V. The fitting results show that current transporting model for the n-BN/p-Si film heterojunctions was the same as Tunnel-Recombination transporting model.