Li-N Codoping Of ρ-type ZnO Based Films And Their Applications In Light-emitting Devices

Zinc oxide （ZnO） has recently been considered as a potential candidate forshort-wavelength optoelectronic devices such as light-emitting devices （LEDs） andlaser diodes （LDs） for its large band gap of3.37eV and large exciton binding energyof60meV. However, the ZnO-based optoelectronic devices applications aredrastically hindered by the difficulties in realizing reliable and reproducible p-typeZnO. This work foucs on the aforementioned problems, the main results wereobtained as follows:1. Obtaining high quality ZnO films with relatively low residual electronconcentration is a fundamental step towards efficient p-type doping and futureapplications in optoelectronic devices of ZnO. A route to high quality ZnO filmswith low electron concentration has been obtained by introducing a thin hightemperature ZnO buffer layer in a plasma-assissted molecular beam epitaxy（MBE）. The residual electron concentration in the films is about1.5×10¹⁶cm^-3,which is comparable with the best value reported (1×10¹⁶cm^-3).2. High responsivity ultraviolet photodetector has been demonstrated based onZnO film. A responsivity of26000A/W has been achieved at8V bias, which isthe highest responsivity ever reported in a semiconductor based UV photodetector. The high responsivity has been attributed to the carrier-trappingprocess at the metal/semiconductor interface, which has been confirmed by theasymmetric barrier height at the two sides of the Au/ZnO interdigital electrodes.3. Based on realization of high quality ZnO films with low electron concetration,Li-N condoping has been employed as the dual-acceptor dopant for the p-typedoping of MgZnO, and p-MgZnO:（Li,N）/n-ZnO single heterostructures have beenconstructed. Obvious near-band-edge （NBE） excitonic emissions coming fromZnO have been observed from the structures at room temperature, and the devicescan work continuously for about6.8h in air ambient under the injection of acontinuous current of20mA. By optimizing the structure, the LEDs can workcontinuously for about97hours, revealing the good reliability of the p-typeZnO-based films obtained by using the Li-N codoping method.4. MgZnO-based heterostructured LEDs have been realized fromp-Mg_0.35Zn_0.65O:（Li,N）/n-Mg_0.20Zn_0.80O structure. Obvious emission peaked ataround355nm has been observed from the heterostructure, which can beattributed to the near-band-edge emission of the n-type Mg_0.20Zn_0.80O layer. Theresults reported in this paper may promise short UV or even deep ultravioletLEDs from MgZnO-based materials.