压力下应变异质结中施主杂质态的Stark效应

对应变GaN/Al_xGa_1-xN异质结系统，考虑理想界面突变势垒，引入简化相干势近似，采用变分法讨论了流体静压力下外界电场对束缚于界面附近的浅杂质态结合能的影响.对GaN为衬底的闪锌矿应变异质结，分别计算了(001)和(111)取向时杂质态的结合能随压力、杂质位置、电场强度以及组分的变化关系.结果表明，杂质态结合能随流体静压力呈近线性变化.电场对杂质态的Stark效应则随杂质位置不同而呈现谱线蓝、红移动.此外，还讨论了在不同压力情况下，Al组分对杂质结合能的影响.当杂质处于GaN材料中且距界面较远时，Al组分的增加使电子的二维特性增强，从而使结合能增大，且压力加剧增幅的增加；当杂质处于Al_xGa_1-xN材料中，Al组分的增加削弱了杂质与电子间的库仑相互作用，故而结合能降低.关键词：xGa_1-xN异质结')" href="#">GaN/Al_xGa_1-xN异质结杂质态压力Stark效应

Stark effect of donor impurity states in strained heterojunctions under pressure

A modified variational method is adopted to investigate the binding energies of the shallow impurity states near the interface of a strained GaN/Al_xGa_1-xN heterojunction by using a simplified coherent potential approximation. The relations between the impurity binding energies and pressure, the impurity position, electric field strength and the Al components are calculated for strained zinc-blende GaN/Al_xGa_1-xN heterojunctions with (001) and (111) orientations respectively. The result indicates that the binding energy of impurity state nearly linearly increases with pressure. The Stark effect on the binding energy as a function of electric field shows blue or red shift in the spectra for different impurity positions. The results corresponding to (001) and (111) orientations are compared. It is found that the effect on the binding energy of Al component is obvious. For an impurity located in the channel side and comparatively far from the interface, a monotonic increase of the binding energies will appear with increasing Al content due to the stronger two-dimensional properties of the electrons, and pressure enhances the increase of amplitude. Whereas for an impurity located in the barrier side, the increase of Al content will weaken the bound between the impurity and the electron to decrease the binding energy.