펄스 레이저 증착(PLD)법에 의한 ZnO 박막 성장과 가전자대 갈라짐에 대한 광전류 연구

Abstract

ArF(193nm) 엑시머 레이저를 이용한 펄스레이저 증착법(PLD)으로 ZnO 소결체를 타켓 증발원으로 하여 Al2O3(0001) 기판위에 성장하였다. 이때 Al2O3(0001)기판의 온도를 400℃로 고정하여 ZnO 박막을 성장하였다. 이때 박막의 결정성은 광발광 스펙트럼과 이중결정 X-선 요동곡선 (DCRC) 으로 부터 구하였다. Hall 효과는 van der Pauw 방법에 의해 측정되었으며, 293K에서 운반자 농도와 이동도는 각각 8.27×1016 cm-3 , 299 cm2/V·s cm2/V·s였다. 광흡수 스펙트럼으로부터 band gap Eg(T)는 Varshni 공식에 따라 계산한 결과 Eg(T) = 3.3973 eV - (2.69 × 10-4 eV/K)T2/(T + 463 K)였다. 10 K일 때 광전류 스펙트럼으로부터 Hamilton matrix (Hopfield quasicubic mode)법으로 계산한 결과 crystal field splitting Δcr값이 0.0041 eV이며 spin-orbit Δso값은 0.0399 eV임을 확인하였다. 10 K일 때 광전류 봉우리들은 n=1일때 A1-, B1-와 C1-exciton 봉우리임을 알았다. 핵심어(Keywords) : 산화 아연(ZnO), 펄스레이저 증착(pulesdlaserdeposition), 광흡수(opticalabsorption), 광전류(photocurrentspectra), 결정장 갈라짐(crystal fieldsplitting), 스핀 자리길 갈라짐 (spin-orbitsplitting)|ZnO epilayer were synthesized by the pulesd laser deposition(PLD) process on Al2O3 substrate after irradiating the surface of the ZnO sintered pellet by the ArF(193 nm) excimer laser. The epilayers of ZnO were achieved on sapphire (Al2O3) substrate at a temperature of 400oC. The crystalline structure of epilayer was investigated by the photoluminescence. The carrier density and mobility of ZnO epilayer measured with Hall effect by van der Pauw method are 8.27×1016cm-3 and 299cm2/V·s at 293K, respectively. The temperature dependence of the energy band gap of the ZnO obtained from the absorption spectra was well described by the Varshni's relation, Eg(T)=3.3973eV-(2.69×10-4eV/K)T2/(T+463K). The crystal field and the spin-orbit splitting energies for the valence band of the ZnO have been estimated to be 0.0041eV and 0.0399eV at 10K, respectively, by means of the photocurrent spectra and the Hopfield quasicubic model. These results indicate that the splitting of the Δso definitely exists in the Γ6 states of the valence band of the ZnO. The three photocurrent peaks observed at 10K are ascribed to the A1-, B1-, and C1-exciton peaks for n=1 The crystal field and the spin-orbit splitting energies for the valence band of the ZnO have been estimated to be 0.0041eV and 0.0399eV at 10K, respectively, by means of the photocurrent spectra and the Hopfield quasicubic model. These results indicate that the splitting of the Δso definitely exists in the Γ6 states of the valence band of the ZnO. The three photocurrent peaks observed at 10K are ascribed to the A1-, B1-, and C1-exciton peaks for n=1