MOCVD Growth And Devices Applications Of ZnO-Based Materials

Zinc oxide (ZnO) is a wide band gap semiconductor with its band gap of 3.37eV and a large exciton binding energy of 60meV at room temperature. Based on its superior properties, ZnO is a promising material for the applications in violet-blue light emitting diodes, ultraviolet photodetectors, shot-wavelength laser diodes, and spin-electronic devices. Thus, much attention and interest in the modern semiconductor have been focused on the research about ZnO material and devices. In this thesis, the MOCVD growth, doping of ZnO thin film and ZnO-based UV photodetector have been studied systematically, as main achievements in the following three aspects:1. The strong correlations between the O/Zn ratio and carbon impurity incorporation have been observed on the ZnO films grown using different conditions. When using N2O as oxygen source, the O/Zn ratio is relatively lower than the case using O2, which leads to high incorporation of unintentional C impurity into the films. Furthermore, the ionization or addition of H2 can significantly enhance the dissociation of N2O, with high O/Zn ratio and film quality improved significantly. The results may provide some experiences and guidance to grow high quality ZnO materials by realization of high O/Zn ratio and suppression of unintentional carbon impurity during the growth process.2. The studies on the in situ doping of indum in ZnO thin films via MOCVD technique have been carried out, and n-type ZnO epilayers with good crystal quality have been achieved. By adjusting the In/Zn mole ratio in reactive gas, the effective control of n-type in situ doping of ZnO has been realized as the electron concentration variation from 1017 to 1020cm-3. The influences of In doping concentration on the crystal, electrical and optical properties of ZnO:In films have been demonstrated in details. Moreover, the Burstein-Moss (BM) and bandgap renormalization (BGR) effects induced by In doping have been studied.3. ZnO-based p-i-n prototype UV photodetector has been successfully fabricated via MOCVD technique. The p-i-n structure consists of Sc doped n-type ZnO single crystal, i-Mg0.3Zn0.7O inserted layer and p-type ZnO:N. This detector shows good rectification characteristics. The photoresponse spectrum indicates UV detectivity with linear response during the short wavelength range. The key role of the i-MgZnO inserted layer, as a barrier layer for minority carrier transport, has been demonstrated by analyzing the energy band. The barrier layer is helpful on impoving and optimizing the performance of UV photodetector.