宽禁带半导体材料强电负性F杂质间隙掺杂研究

The difficulty in high efficiency p-type doping of wide bandgap semiconductors is the key factor that limits the further development of the related devices, and is an important scientific problem that highly needed to be solved in semiconductor area. Due to the very low valence band maximum, the traditional p-type dopants are difficult to generate sufficient high hole concentration. To solve such problems, we proposed a novel method to realize the p-type doping of wide bandgap semiconductors, namely, by introducing fluorine (F) impurities into the interstitial lattice locations of the materials. As compared with the traditional acceptors, F atoms have very high electronegativity, which are easier to capture electrons and thus forming holes in the valence bands; the theoretically calculated ionization energies of F acceptors in wide bandgap materials are much lower than that of the traditional acceptors, and therefore it is easier to obtain higher room temperature hole concentration. This project will systematically develop the method for interstitial F doping, and investigate the doping types, energy levels, and hole concentrations induced by F doping, and provide a more efficient way for enhancing the hole concentration of p-type wide bandgap semiconductors.

宽禁带材料的高效p型掺杂困难是制约相应器件进一步发展的一大障碍，也是半导体领域亟待解决的一项科学难题。由于宽禁带材料的价带顶位置很低，传统的p型杂质难以实现高的空穴浓度。为解决这些问题，本项目创新性的提出了向晶格中的间隙位引入强电负性F杂质实现宽禁带材料p型掺杂的新方法。相比于传统的受主型杂质，F杂质具有非常强的电负性，更容易夺取电子而在价带形成空穴，其理论计算的电离能比传统的受主型杂质低很多，更容易实现高的室温空穴浓度。项目拟对间隙F的掺杂方法、间隙F杂质在宽禁带半导体中的导电类型、能级位置、所能实现的载流子浓度等进行系统性的研究，为提高p型宽禁带半导体材料的空穴浓度提供更为有效的解决途径。

宽禁带材料的高效p型掺杂困难是制约相应器件进一步发展的一大障碍，也是半导体领域亟待解决的一项科学难题。本项目开展了宽禁带材料强电负性杂质离子注入掺杂的研究。首先我们通过脉冲金属有机物气相沉积（MOCVD）的方法制备了高质量的AlN单晶薄膜，位错密度降低到了约108 cm-2量级。其次开展了F离子注入GaN的研究。对F离子注入进行了模拟，发现使用单一能量注入会导致离子在材料中呈高斯分布。为得到较均匀的深度分布，需要多种能量和剂量组合的注入方式。实验发现离子注入会对材料造成明显的晶格损伤，导致材料的电学和光学性能受到严重损坏，退火后也不能完全恢复。实验并没有得到预期中的P型掺杂，反而发现退火后的GaN呈N型导电，可能是由于离子注入导致太多空位的产生。本项目对研究强电负性杂质在宽禁带半导体材料中的掺杂提供了研究基础，但要实现P型掺杂，需要进一步探索合适的注入和退火条件。