硅中金受主能级在单轴应力下瞬态电容的研究

用恒定温度下瞬态电容法研究了硅中金受主能级在沿〈100〉,〈110〉,〈111〉晶向单轴应力作用下的能级移动。考虑到硅的导带在单轴应力下的分裂,导出了单轴应力下深中心中电子发射率的公式。根据该式和发射率的实验数据以及切变畸变势常数Ξ_u,求出了金受主能级激活能随应力的改变。在实验应力范围内(0—9kbar),激活能与应力成线性关系。当应力平行于〈110〉〈111〉晶向时,激活能随应力改变的斜率分别为α_<110>=-3.2±0.6meV/kbar,α_<111>=-0.3±0.6meV/kbar;当应力平行于〈100〉晶向,若取Ξ_u=9.2eV,α_<100>=-5.8±0.8meV/kbar,若取Ξ_u=11.4eV,α_<100>=-5.3±0.8meV/kbar,α表现出强烈的各向异性。进一步确定了金受主能级相对于零压力下导带底的绝对移动的压力系数。若取Ξ_u=9.2eV,这些系数分别为S_<100>=-1.3±0.8meV/kbar,S_<110>=0.7±0.6meV/kbar,S_<111>=-0.7±0.6meV/kbar。如取Ξ=11.4eV,则S_<100>=-3.5±0.8meV/kbar,S_<110>=0.0±0.6meV/kbar,S_<111>=-1.0±0.6meV/kbar。同一组的三个绝对移动值之间的偏离都超过了实验误差这一事实,说明了金中心具有立方对称性,同时中性金与带负电的金的基态都是非简并的可能性很小。 关键词：

A STUDY OF TRANSIENT CAPACITANCE OF GOLD ACCEPTOR ENERGY LEVEL IN SILICON UNDER UNIAXIAL STRESS

Using the method of transient capacitance at constant temperature, the shift of gold acceptor energy level in silicon under 〈100〉,〈110〉,〈111〉 uniaxial press has been studied. Considering the split of conduction band caused by uniaxial stress, a formula for electron emission rate from deep center to conduction band has been derived. With this formula and experimental data of emission rate and reported tangential deformation potential constant Ξ_u ,the active energy of gold acceptor under various uniaxial stress has been determined. In the range of experimental stress (0-9 kbar), a linear dependence of active energy on stress has been found. When uniaxial presses are parallel to 〈110〉,〈111〉 crystal orientations, the proportionality constants are α_<110>=-3.2±0.6 meV/kbar, α_<111>=-0.3±0.6 meV/kbar respectively. When uniaxial press is parallel to 〈100〉 crystal orientation and if we take Ξ_u = 9.2 eV, α_<100>= -5.8± 0.8 meV/kbar, or if Ξ_u =11.4 eV, α_<100>=-5.3± 0.8 meV/kbar. The changes of active energy are strongly anis-otropic. Further more, we have determined the shift coefficients of gold acceptor level in the presence of uniaxial stress relative to the bottom of conduction band in the absence of uniaxial stress. When Ξ_u=9.2 eV, the coefficients are S_<100>=-1.3±0.8 meV/kbar, S_<110>=0.7±0.6 meV/kbar, S_<111>=-0.7±0.6 meV/kbar respectively, when Ξ_u=11.4 eV, the values are S_<100>= - 3.5± 0.8 meV/kbar, S_<110> = 0.0±0.6 meV/kbar, S_<111>=- 1.0±0.6 meV/kbar. Deviations among three coefficients of each group are larger than uncertainty of experiments. Thus, the possibility that gold centers in silicon have cubic symmetry and at the same time both negatively charged and neutral gold centers have nondegenerate basic states is quite small.