A Study On Properties Of N-doped ZnO Film

ZnO is a II-VI compound semiconductor with a wide direct bandgap of 3.3eV atroom temperature, exciton binding energy of 60meV, and a hexagonal wurtzite structureof space group P63mc. Its lattice parameters are a = 0.325nm and c = 0.521nm. Due totheir excellent physical and chemical properties, they can be integrated with somematerials readily. In recent years, the researches and developments of ZnO films haveattracted great attention and interest from researchers and the industry.The key technique to realize the ZnO applied in photoelectricity device is to producethe p-type ZnO film with low resistance. However, like other wide band gap materials,while easy for n-type doping, ZnO displays significant resistance to the formation ofshallow acceptor levels for p-type doping. The main reasons are as follow: the raise ofMadelung energy will make the structure of the lattice unstable;the Zn interstitials andO vacancies in the ZnO film would compensate electrons and low solubility of thedopants;the normal way of p-type dopants is the compounding way by both group V (N,P, As) and co-dopants with n-type donor.To produce ZnO film there are a few methods, each of which has merits and defects.Considering the current conditions and the demand for the stability of the P-type dopingin our task, we put the N-doping of ZnO film into three steps. Firstly, the ZnO film wasproduced on glass and silicon by magnetron sputtering;secondly, N ion was implantedinto ZnO film based on silicon;lastly, the film was annealed under N eviroment toachieve the purpose of doping.The uniformity of the thickness of the film martial deposited by RF magnetronsputtering was checked by profilometer. The optical transmission spectra were recordedwith a UV-VIS spectrophotometer. Films of different stages were observed by SEM tofind their exterior configuration. The crystal structure of the films were analyzed byXDR and the electrics capability of the films were tests by Hall Measurements.It is found that the thickness of the ZnO film impartial which was deposited by RFmagnetron sputtering is relatively uniform and exhibit a preferential orientation alongc-axis, so the quality of the films were really good;the films deposited on glass showhigh transparency and the optical band gap of film determined from the slope of thelinear plot is estimated to be about 3.45eV;the surface of the film was damaged afterion implantation, but it would recover with the enhance of the anneal temperature andextending of the length of anneal time, and the surface of the films will be more smoothand compact. The quality of crystallinity of film would emerge a peak with theenhancement of the the time and temperature and the FWHM went to stability;Hallmeasurements show the change of p-type samples would be divided into two areas.Some would belong to weak p-type under 800 centigrade and it doesn't relate too muchto the time of anneal while a higher carrier concentration would show if the annealingtemperature was raised and the length of annealing time was prolonged when thetemperature is up 800 centigrade. A unusual area showed when the length of annealingtime is about 3 minutes, the reason of which should be discussed further.