Study On AZO Thin Films Fabricated By Atomic Layer Deposition And Surface Passivation On Crystalline Silicon

AZO film that zinc oxide doped with aluminum elements is an excellent transparentconducting films because of high carrier concentration, good transmittance, lowresistivity close to the indium tin oxide thin films andl ow cost. It is the most promisingalternative to ITO film to apply on these field such as light emitting diodes, transistors, solarcells and so on. In this paper Al-doped zinc oxide (AZO) films were prepared on quartzsubstrates by using atomic layer deposition. The growth rate, surface morphology, structure,composition and electric properties were studied by using spectroscopic ellipsometer, atomicforce microscopy, X-ray diffraction, Raman spectroscopy, UV-visible spectrophotometer, PLspectroscopy, X-ray photoelectron spectroscopy and Hall measurement. AZO thin films wereused to surface passivate of crystalline silicon and the mechanism of surface passivate wasdiscussed.The effect of various ratio of aluminum and zinc on AZO thin films were studied. As theradio of aluminum and zinc increased, the (002) diffraction face of AZO thin films wasinhibited by Al doping, the average grain size decreased, grain boundaries and defects in filmsincreased, and the resistivity first raised, and then decline. When the ratio of aluminum andzinc is1:9, the resistance of AZO film was lowest. All of AZO film had a high transmittanceof>80%in visible light range. The UV absorption edge had a blue shift phenomenon andoptical band gap increased with the radio of aluminum and zinc increasing.AZO thin film infuenced by deposition temperature were studied. As depositiontemperature increased, the growth of (100) crystal plane of AZO with wurtzite strcture wasinhibited and the (002) crystal plane was promoted, which showed c axis preferred orientation,and crystal quality first increased and then decreased. When the deposition temperature is150℃AZO film had a best crystal quality with lowest defect concentration and had lowestresistance,4.61×10-4cm. All of AZO film had a high transmittance of>80%in visible lightrange and the UV absorption edge had a blue shift with deposition temperature increasing.AZO film passivated p-type crystalline silicon, passivated process raised minority carrierlifetime from4.27μs to49.97μs, which showed greatly improve on minority carrier lifetime,about eleven times. The surface recombination velocity decreased from Seff≦5.3×103cm/sto Seff≦500cm/s by AZO surface passivation that reduced by an order of magnitude. Theresults show AZO films had a excellent passivation effect on crystalline silicon surface. Thepassivation mechanism of AZO film passivated p-type crystalline silicon is geared tochemical passivation.