【摘要】 将Se离子注入到ZnSe晶体中,用深能级瞬态谱仪(DLTS)测量了注Se~+前后ZnSe晶体中深能级的变化,发现在ZnSe中经常出现的分别位于导带下0.30eV和0.33eV的两个能级在注Se~+和退火后消失。这个结果进一步证实了Beomi等人提出的以上两个能级分别与Se双空位和包含一个Se单空位的复合体有关的论点。同时注Se~+后在导带下0.34eV出现一个新的能级,其电子俘获截面明显区别于0.33eV能级。该能级可能与Se填隙原子或占Zn位的反位Se原子有关。更多还原

【Abstract】 ZnSe has the potential to be used to make blue LED because it has wide band gap, and its strong blue exciton luminescence is observed even at the room temperature. The main obstruction in practice is that the p-type ZnSe with low resistivity is difficult to produce due to self-compensation. It seems that the self-compensation effect is related to the native defects originating in nonstoich-iometry during crystal growth. The two electron traps which are located at 0.30 and 0.33eV (labeled as A and B thereafter) below conduction band are commonly observed in ZnSe. Some authors suggested that these traps be associated with Se vacancies.In search of the nature of these two traps, Se ion implantation into unintentionally doped .ZnSe was carried out. The implanting energy of 180keV, dose of 1×1014cm-2, and the target temperature of 77K were used. .For comparison, another ZnSe sample was implanted with Kr+ under similar conditions.The post-annealing was carried out a: 350℃ for 20min. A Si3N4 layer of 2500A was formed on the top of the sample before annealing.After annealing Au/ZnSe -Schottky barrier was made on the implanted layer for deep level transient spec-troscopy(DLTS) measurement. The sample conditions and concentration ND of the net donor are given in Table 1.Fig.1 shows the DLTS spectrum of ZnSe samples. Fig.2 shows the thermal emission rates as a function of reciprocal temperature for four electron traps measured by DLTS. The apparent thermal activation energy Ea and concentration N, of the deep levels observed in the samples were determined and presented in Table 2. The centre B disappeared after Se+ implantation, and centre A disappeared after annealing. A new centre C Was induced by Se+ implantation. The electron capture cross section of the centre C is, much larger than that of centre B.The results presented above can be explained as follows. During the implantation (with Se+ or Kr+), plenty of Se vacancies and Se interstitials was produced by ion collisions. As temperature is raised to room temperature, the samples experienced a partly annealing, especially for Se vacancies. Most of Sc vacancies produced during the implantation combined to form Se divacancies or recombined with Se interstitials. Then after returning to room temperature, single Se vacancies should not exsist at all, but the existence of Se divacancies is still plausible. After annealing, the empty lattice sites in Se divacancies could be occupied by Se interstitial, considering the fact that there were a lot of excess Se in Se+ implanted sample. So the concentration of Se divacancies is reduced obviously. Therefore, it is reasonable to relate the trap B to a complex involving a single Se Vacancy, and the trap A to Se divacancies. The results obtained provide a piece of moie direct experimental evidence for Besomi’s argument.The nature of the centre C is probably related to Se interstitial whereas centre D probably is due to the irradiation damage.更多还原