Ga Dopant Induced Band Gap Broadening and Conductivity Enhancement in Spray Pyrolysed Zn0.85Ca0.15O thin Films

Ga doped Zn0.85Ca0.15O thin films were prepared by spray pyrolysis method and studied the impact of Ga doping concentration on the physical properties of these films. XRD analysis confirmed the structural purity and polycrystalline nature of the films and composition analysis verified the incorporation of dopants in the structures. Optical transmission in the visible range initially increased and at higher Ga concentration decreased in accordance with the crystalline quality. Energy gap increased with doping percentage due to Burstein-Moss effect arising from the increase in carrier concentration. Ga doping resulted in enhanced electron concentration and consequently obtained lower resistive n type thin films. At higher doping level, electron density decreased due to the limit of solid solubility and hence conductivity slightly decreased but energy gap increased due to the extended localization arising from the poor crystallinity. Mobility decreased with doping due to the increased ionized impurity scattering at lower dopant concentration and due to intra-grain cluster scattering at heavy doping.采用喷雾热解法制备了镓（Ga）掺杂Zn₀.₈₅Ca₀.₁₅O薄膜，并研究了镓掺杂浓度对该薄膜物理性能的影响。X射线衍射（XRD）分析证实了薄膜具备结构纯度与多晶特性，成分分析验证了掺杂剂已成功掺入薄膜晶格结构中。可见光波段的光学透射率先随镓掺杂浓度升高而提升，当掺杂浓度较高时，透射率与薄膜晶体质量的变化趋势一致而下降。禁带宽度随掺杂比例升高而增大，这是由载流子浓度提升引发的布斯坦-莫斯（Burstein-Moss）效应所致。镓掺杂可提升薄膜的电子浓度，因此制备出了低阻n型薄膜。当掺杂浓度过高时，受固溶度极限限制，电子密度会出现下降，因此电导率略有降低；但由于结晶质量变差引发的局域化扩展，禁带宽度反而有所提升。载流子迁移率随掺杂浓度升高而下降：低掺杂浓度下，迁移率下降源于电离杂质散射加剧；重掺杂时，则归因于晶粒内团簇散射效应。