Silicon-based ZnO (CdZnO) Films And Light-emitting Devices

With a wide direct band gap of 3.37 eV and large exaction binding energy of 60 meV at room temperature, ZnO is considered as one of the most promising materials for ultraviolet (UV) optoelectronics. The band gap of CdO is 2.3 eV. ZnO is expected to be the photolectric material in visible region when alloyed with CdO. In this paper the photoluminescence of silicon-based ZnO (CdZnO) films has been studied. Moreover, light-emitting devices were prepared and the electroluminescent of them has been investigated. The primary achievements are as follows.1. ZnO films were deposited on the silicon subtract by direct current sputtering. The effect of RTA conditions on photoluminescence has been investigated. It is found that the ZnO film received the RTA at 800℃under Ar ambient shows much stronger PL than that received the RTA at 800℃under O2 ambient. With the post-RTA at 60℃under Ar ambient, the ZnO film received the RTA at 800℃under O2 ambient exhibits ultraviolet (UV) PL as intense as that of the ZnO film received the RTA at 800℃under Ar ambient. It is supposed that a certain amount of negatively charged oxygen species exist on the surface of the ZnO film received the RTA under O2 ambient, leading to a build-in electric field. This in turn reduces the recombination probability of photo-generated electrons and holes, resulting in the suppressed NBE PL.2. With the ZnO and SiO2 acted as the semiconductor and insulator, the ZnO-MIS device was prepared on the n+-Si substrate by sputtering method. Under forward bias, the ZnO-MIS structure demonstrates random laser when the thickness of SiO2 is at-12 nm. With SiO2 thickness decreased to-9 nm, there is only spontaneous emission from ZnO-MIS structure. Only when the SiO2 is thick enough the random laser can be produced under forward bias with high concentration carriers accumulated in the Zn0/SiO2 interface.3. The CdZnO films were deposited by radio frequency sputtering and the effect of RTA conditions on crystal structure, surface morphology and photoluminescence has been investigated. It is shown that with the increase of RTA temperature and RTA time, more voids are formed in the films due to the volatilization of Cd. In the meantime, the PL peak of CdZnO shows blue-shift. The CdZnO/SiO2 (MgO)/P+-Si structure was fabricated and the device exhibits the near-band-edge (NBE) emission from CdZnO.