The Influences Of Hydrogen In ZnO Film Growth And ICP Etching In ZnO Nano-patterning

Since the room-temperature lasing phenomenon in zinc oxide(ZnO)has been observed in 1997,the research from world-wide on the optical and electrical properties of ZnO related semiconductors has lasted for twenty years.Currently the boom continues,yet with decreased enthusiasm.It is still difficult to attain stable,controllable Zno film with high quality.Recently,researchers have concentrated more on the investigation of the intrinsic physical properties of ZnO.In the research of wide band gap semiconductors,H(hydrogen atom or molecule)is widely used in GaN materials fabrication and performance control.Hydrogen is also considered as an important p-type dopant in GaN which determines the electrical properties in wide band gap semiconductors.As well as in ZnO materials,hydrogen acts as shallow donor and has great contribution on growth,structure and electrical properties in ZnO material.Meanwhile,plasma etching is a necessary process in ZnO film growth.Because of the small corrosion selectivity ratio between ZnO sample and the dielectric protective film,surface morphology and the optical properties of ZnO thin film is unavoidable changed.In this paper,the effect of hydrogen on different MO sources was studied in the process of ZnO growth.We also have studied the mechanism of the fine structure emission in the temperature dependent photoluminescence spectra of ZnO samples with plasma etching process treated.Detailed results are listed below:(1)We have studied the effect of hydrogen addition on different MO sources in ZnO film MOCVD growth.The quality of the sample was greatly improved due to H2 when dimethyl zinc used as zinc source.The existence of hydrogen atoms will promote O atoms desorbed from the growth surface and thus improve the migration ability of the atoms on the sample surface.Either O2 or N20 used as the oxygen source,there are strong D and G peaks which are related to carbon clusters observed in the samples without H2 treated.H2 addition could suppress carbon impurity.The Hall measurements also verify the improvement of the lattice quality.The quality of ZnO lattice was decreased with H2 added while diethyl zinc used as zinc source,due to C2H4 and intermediate compounds Zn-H bond formed via p dehydrogenation of DEZn are conducive to reduce carbon contamination from metal organic source.But hydrogen adding will suppress beta dehydrogenation reaction,thereby decreasing the quality of ZnO samples.While nitrous oxide used as oxygen source,the D and G peaks related with carbon clusters are weaken obviously with hydrogen added.And when O2 used as the oxygen source,added hydrogen significantly enhance the D and G peaks' intensity.The result is consistent with that given by atomic force microscopy(AFM).In both case when dimethyl zinc or diethyl zinc is used as zinc source,the addition of H2 suppress the formation of non-radiative recombination centers and improve the optical properties of ZnO samples.(2)We studied TD-PL spectra of the nano patterned ZnO sample treated by plasma etching.Furthermore,we studied the origin and mechanism of fine structure emission in PL spectrum.The three peaks located at around 3.3eV are identified as Y lines,which has been widely reported and ascribed to structural defects.The preferential etching of O atoms on the surface of ZnO by ICP plasma etching lead to the formation of large amounts of interstitial zinc,while the confinement effect of nano patterned ZnO window results in the agglomeration of interstitial zinc at the boundary and clusters formed.The formed Zni small clusters behavior as deep donors,and may be related to the observed Y-lines.Theoretical calculations show that the zinc number in the in Zni cluster will lead to the change of the donor energy level and form three different levels of donors,resulting in the Y emissions have a certain energy interval.The three peaks located at around 3.28eV show the exciton characteristic and are not reported by pervious work.The changes of energies and intensities of the emissions all agree well with the Y-lines,indicating they all share the same donors.Because of the deep energy leval,we suggested that single donor or acceptor is not the origin of the emission.Considering the relation with Y lines and the formation of eA with temperature increased,we believe the emissions are related with donor-acceptor complex(DAX).Besides Zni clusters as three donors with different energy levels,intrinsic zinc vacancy clusters may be the origin of the shallow acceptor.The three emissions at around 3.22eV are in the area of donor-acceptor pairs.Temperature and power depend PL both show that the emissions have DAP characteristic and change into eA nearby with temperature increased.The energy position and intensity of the emissions have the same change with Y lines.It shows that the DAP emissions shares the same donors with DAX and Y lines,but the acceptor's energy level is deep.It may be related with single Vzn or zinc vacancy related complex.