Growth Of ZnSe Films By Chemical Activated Hot Wall Epitaxy And The Property Characterization

As an importmant direct wide-band-gap II-VI semiconductor, ZnSe has direct band gap transition, high exciton bound energy and excellent optical, electrical properties, which makes it a kind of well-known luminous, non-linear optical, laser material and having a wide application in the fabrication of blue-green light diodes, nonliear optical-electronic components and infrared devices. For the difficulties in single crystal growth, these devices are mostly produced by ZnSe film and polycrystal at presen. In this paper, the preparation, structure and properties of ZnSe films are studied.The chemical activated hot wall epitaxy method was used to grow ZnSe. Using compound Zn(NH₄)₃Cl₅ as transport agent, the ZnSe film is prepared on Si(111) substrates using Zn and Se sources. The ZnSe films were characterized by SEM, EDS and PL spectra for their morphologies, composition and luminescence properties. Also the influences of process parameters on the morphologies and propertis of the film were studied. The results indicate that the hot wall temperature and the deposition time were the main factor influencing the morphology of ZnSe films. The compound Zn(NH₄)₃Cl₅, as the chemical activated agent, was revealed to promote the growth of ZnSe with the stoichiometric composition by avoiding the kinetics limitation of the congruent sublimation conditions.In order to choose the optimum growth parameters, the thermodynamic analysis of the Zn-Se-Zn(NH₄)₃Cl₅ system is conducted in the crystal growth of ZnSe crystal from Zn and Se sources with the help of the transport agent Zn(NH₄)₃Cl₅. The optimum vapor growth condition is determined using the partial pressure values of each compounent in the system, which is calculated theoretically at different temperature and for different transport agent concentration. From the theoretical results, an intrinsic temperature range, which has no realationship with the concentration of transport agent, is determined in the Zn-Se-Zn(NH₄)₃Cl₅ system. The stiochiometric proportion of ZnSe grown in this range is 1:1 and the crystal will be rich in Zn or Se if the growth temperature higher or lower than this intrinsic temperature range.