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采用低压金属有机化学气相外延(LP-MOCVD)法生长Mg掺杂p型GaN薄膜,利用高分辨X射线衍射(HRXRD)技术研究不同退火时间对GaN薄膜中外延应变的影响。研究发现应变状态随退火时间变化而发生改变。退火前水平方向为压应变。在小于最佳退火时间(15min)的时间范围内进行退火时,由于受杂质Mg在退火过程中热扩散、替位行为引起的晶格畸变以及受主中心与价带之间的电子跃迁引起的电子效应等多种因素的影响,水平应变状态由压应变向张应变转变且随时间增加应变逐渐增强。退火时间增至30min时,由于N空位增多和复合体MgGa-VN的形成以及热应力等因素的多重影响,应变状态转变为压应变。
Mg-doped p-type GaN films were grown by low pressure metal-organic chemical vapor deposition (LP-MOCVD) and the effect of different annealing time on the epitaxial strain in GaN films was investigated by HRXRD. The study found that the strain state changes with the annealing time changes. The horizontal direction before annealing is the compressive strain. When annealed in less than the optimal annealing time (15min), due to the thermal diffusion of impurity Mg during annealing, the lattice distortion caused by the substitution behavior and the electron transition between acceptor center and valence band Electronic effects and other factors, the horizontal strain state changes from compressive strain to tensile strain and increases gradually with time. When the annealing time increases to 30min, the strain state changes to compressive strain due to the multiple influence of N vacancies and the formation of MgGa-VN complex and thermal stress.