Optimization of Zn_1−x−yMg_xAl_yO Film Properties to Use in Deep UV SAW Photodetector

Abstract

The maximum of spectral sensitivity of ZnO based photodetectors can be shifted to deep UV photon range of ~250 to 300 nm by Mg dosing [1, 2]. However heavily Mg doped ZnO shows very poor conductance and optical properties, which limits its use as a sensitive element of deep UV SAW photodetector. The simultaneously doped ZnO by Mg and Al atoms may assist in tuning electrical, optical and structural properties of ZnO in wide range and opens the possibility to use Zn_1−x−yMg_xAl_yO films for deep UV detector integrated to SAW device. Apart from dopant related aspects the structural and optical quality of a film prepared by PLD method is heavily influenced by the film/nanostructure growth temperature and oxygen pressure. We study optical, structural, lattice vibration modes and photoelectric properties of Zn_1−x−yMg_xAl_yO films on LiNbO₃ substrates designed by PLD method at different oxygen pressure and growth temperatures to optimize their properties for using as a deep-UV-sensitive element of surface acoustic wave (SAW) photodetector. The optical absorption band edge for optimized Zn_0.52Mg_0.19Al_0.007O/LiNbO₃ film was shifted to 320 nm and the corresponding photodetector demonstrates high sensitivity and fast photoelectric response towards 248 nm laser light.