Electronic states of site-controlled impurity layrs at semiconductor interfaces and its applications to control of band discontinuities

1.为了从理论上预测异质界面的能带不连续性，我们编制了基于sp^3s^*基的自洽紧束缚方法程序。在这种方法中，原子轨道能用界面上的电子电荷计算的感应静电势来修正。用该程序计算了GaAs/AlAs界面的价带不连续性DELTAE_v。计算得到(100)和(110)界面的DELTAE_v=0.51 eV，(311)A界面的DELTAE_v=0.50 eV。对于不同的界面取向，即使是高折射率界面，界面上的DELTAE_v几乎都是恒定的。计算出在GaAs/Si(2ml)/AlAs界面处的DELTAE_v=-1.36 eV[(100)-As界面]，2.1 eV[(100)-Ga界面]，0.35 eV[(110)界面]，-0.12 eV[(311)A-As界面]，1.67 eV[(311)A-Ga界面]。DELTAE_v由Si诱导的界面偶极子决定，并强烈依赖于界面取向。计算出(100)As/InAs(1ml)/AlAs界面的DELTAE_v=0.50 eV，这实际上等于没有插入层的GaAs/AlAs界面的DELTAE_v=0.51 eV。应变InAs单层的插入改变了GaAs/AlAs界面的价电荷密度细节，但不改变DELTAE_v。计算结果与我们对分子束外延样品的实验测量结果是一致的。

1. To predict band discontinuities at hetero-interfaces theoretically, we constructed a program for the self-consistent tight-binding method with the sp^3s^* basis. In this method, the atomic orbital energies are modified with the induced electrostatic potentials calculated from the electronic charges at interfaces.2. Using this program, we calculated valence-band discontinuities, DELTAE_v, at the GaAs/AlAs interfaces. The calculation gives DELTAE_v=0.51 eV at the (100) and (110) interfaces, and DELTAE_v=0.50 eV at the (311) A interface. DELTAE_v at the GaAs/AlAs interface is almost constant for various interface orientations, even for the high-index interfaces.3. DELTAE_v at the GaAs/Si (2ML) /AlAs interface is calculated to be ; DELTAE_v=-1.36 eV [ (100)-As interface] , 2.1 eV [ (100)-Ga interface] , 0.35 eV [ (110) interface] , -0.12 eV [ (311) A-As interface] , and 1.67 eV [ (311) A-Ga interface] . DELTAE_v is determined by the Si-induced interface dipole and depends strongly on the interface orientations.4. DELTAE_v at the (100) GaAs/InAs (1ML) /AlAs interface is calculated to be 0.50 eV,which is practically equal to DELTAE_v=0.51 eV at the GaAs/AlAs interface with no insertion-layrs. The insertion of the strained InAs monolayr changes the detail of valence charge density at the GaAs/AlAs interface but does not change DELTAE_v. The result of calculation is consistent with our experimental measurement for the MBE-grown samples.