HRXRD研究退火时间对Mg掺杂P型GaN薄膜应变状态的影响

High-resolution XRD study of the effect of the annealing time on strain in Mg doped p-type GaN epitaxial films

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 epitaxial thin films were prepared by low pressure metal-organic chemical vapor deposition （LP-MOCVD）. The effect of annealing time on the epitaxial strain in GaN films was detailedly studied by high-resolution X-ray diffraction （HRXRD）. It was found that strain states would change with annealing time. Before annealing, the strain on the horizontal direction was compressive. When the annealing time was lower than the optimal annealing time, 15 min, the horizontal strain transferred from compressive strain to ten- sile strain, and enhanced with the increase of annealing time, which was the result of the lattice distortion due to the thermal diffusion and displacement of Mg impurity, and the electronic effects arose from the electron transition between the aeeeptor center and valence band. When annealing time increased to 30min, strain trans-formed to compressive strain due to the effects of increased N vacancy, formation of MgGa-VN, thermal strain, and so on.