The Study Of Fabrication And Properties Of P-type ZnO Thin Films By Al-N Co-doping Method

Zinc oxide(ZnO) is a II-VI compound semiconductor with a wide direct band gap of 3.37eV at room temperature. It has an exciton binding energy of 60meV and high exciton emission efficiency of 300cm^-1. Due to these features, ZnO has become a promising candidate for applications in LED and LDs as a short-wavelength material. Generally ZnO occurs as a n-type conduction with good electronic properties by doping Al, Ga atoms. However, it is difficult to achieve p-type conduction because of the low solubility of the dopant and high self-compensating process upon doping due to its intrinsic donor defects (Zn_i or Vo). Yamamoto predicted theoretically that p-type ZnO could be obtained by simultaneous co-doping using reactive donor co-dopants (e.g. Al, Ga and In) and acceptor co-dopants (e.g. N) because the former could enhance the incorporation of N acceptors and give rise to shallower N-acceptor levels in the band gap of p-type co-doped ZnO crystal as well. M. Joseph had successfully fabricated p-type ZnO crystal by Ga-N and Al-N co-doping methods, respectively.Magnetron sputtering technique is a wisely spreading application method in fabricating p-ZnO thin films because it can use different sputtering gas and different targets during the doping process.The state key laboratory of silicon materials of Zhejiang University is one of the earliest groups devoted in the research of ZnO thin films. With the instruction of Dr. Ye, we firstly realized p-ZnO thin films by Al-N co-doping method using Magnetron sputtering technique, and discussed the doping mechanism by XPS and SIMS methods. Further, we studied the effect of substrate temperature, oxygen partial pressure ratios and post annealing on Al, N codoping p-ZnO thin films by XRD, SEM, AFM, SRP, Hall, etc. The study shows, under deposited in 400℃ substrate temperature and 85% oxygen partial pressure ratios, p-ZnO thin film has better crystalline structure and electrical properties, resistivity ρ = 24.5Ω·cm, carrier concentration n_p=7.48×10¹⁷cm^-3, mobility μ=0.341 cm²/V·s。...