FABRICATION OF p-TYPE ZnO BY RF SPUTTERING TECHNIQUE

ABSTRACT

High purity targets of ZnO (99.99%) and AlN (99.999%) were used in the sputtering process to prepare (Al-N) codoped ZnO thin films using RF sputtering technique. The effect of preparation conditions on the structural, optical and the electrical properties of the prepared films were investigated. X-ray diffraction (XRD), AFM, FESEM, ultraviolet and visible (UV-V) transmission spectrometer, PL and Raman spectroscopy were employed for sample characterization. The Hall Effect technique was used for the measurement of resistivity, carrier concentration, Hall mobility and the conduction type of the produced films. The X-ray diffraction revealed the preferred (002) phase c-axis orientation of the deposited films while the UV-V spectra analysis yielded the energy band gap of the films in the range of (3.24 – 3.52) eV. Raman spectra and EDX analysis proved the presence of nitrogen in the film that could have been incorporated during the fabrication process. The observed peak at 276 cm

-1 of Raman spectra was attributed to nitrogen while the peak at 578.58 cm-1 was attributed to A1 (LO) mode of the AlN doped ZnO films. The films with p-type conductivity have been achieved at the fabrication conditions of 80 (N2): 20 (Ar) gas ratio, (175-225) W RF power of ZnO target and (90-100) W RF power of AlN target. The mechanism for the p-type conductivity was suggested to be attributed to the formation of (N)O acceptor and N-Al-N complex acceptor states at the shallow energy levels in the energy band gap of the ZnO. With the optimum fabrication conditions, the highest carrier concentration of 3.68 × 1021 cm-3 and the highest carrier mobility of 117 cm2V-1s-1 of p-type ZnO has been achieved in the present work, which subsequently shown to have formed good p-n junction and MOS structure devices.

ABSTRAK

Sasaran ZnO (99.99%) dan AlN (99.999%) ketulenan tinggi digunakan dalam proses percikan untuk menyediakan filem nipis ZnO terdop bersama (Al-N) menggunakan teknik percikan RF. Kesan keadaan-keadaan penyediaan ke atas sifat-sifat struktur, optik dan elektrik filem dikaji. Belauan sinar-X (XRD), AFM, FESEM, spectrometer pemancaran ultra lembayung-nampak (UV-V), PL, spektroskopi dan Raman digunakan untuk pencirian sampel. Teknik Kesan Hall digunakan bagi pengukuran kerintangan, kepekatan pembawa, kelincahan Hall dan jenis kekonduksian filem yang dihasilkankan. Belauan sinar-X menunujukkan filem cenderung termendap sebagai fasa (002) berorientasikan paksi-c sementara analisa spektra UV-V menghasilkan jurang jalur tenaga filem dalam julat (3.24 – 3.52) eV. Spektra Raman dan analisa EDX membuktikan kehadiran nitrogen dalam filem yang berkemungkinan tergabung semasa proses fabrikasi. Puncak ternampak pada 276 cm

 

-1 dari Raman spektra berkait dengan nitrogen sedangkan puncak pada 578.58 cm-1 berkait dengan mod A1 (LO) dari filem ZnO terdop AlN. Filem kekonduksian jenis-p diperolehi dengan keadaan fabrikasi nisbah gas 80 (N2): 20 (Ar), kuasa RF sasaran ZnO pada (175-225) W dan kuasa RF sasaran AlN pada (90-100) W. Mekanisme bagi kekonduksian jenis-p dicadangkan berkait dengan pembentukan keadaan-keadaan penerima (N)O dan penerima kompleks N-Al-N pada paras-paras tenaga cetek dalam jurang jalur tenaga ZnO. Dengan keadaan fabrikasi optimum, kepekatan pembawa tertinggi (3.68 × 1021 cm-3) dan kelincahan pembawa tertinggi (117 cm2V-1s-1

) bagi ZnO jenis-p dihasilkan dalam kajian ini, yang kemudiannya menunjukkan kebolehan bagi pembentukan peranti-peranti simpang p-n dan struktur MOS yang baik.