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处的能带不连续性，我们编制了一个sp^3s^* 基的自洽紧束缚方法程序。在该方法中，原子轨道能量由界面电荷计算的感应静电势修正.利用这个程序，我们计算了GaAs/AlAs界面处的价带不连续性Δ E_v。计算给出在（100）和（110）界面处的Δ E_v=0.51 eV，以及在（311）A界面处的Δ E_v=0.50 eV。GaAs/AlAs界面的Δ E_v对于不同的界面取向几乎是恒定的，即使对于高折射率界面也是如此. GaAs/Si（2 ML）/AlAs界面处的Δ E_v计算为：Δ E_v=-1.36eV [（100）-As界面]、2.1eV [（100）-Ga界面]、0.35eV [（110）界面]、-0.12eV [（311）A-As界面]和1.67eV [（311）A-Ga界面]。Δ E_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）GaAs/InAs（1 ML）/AlAs界面处的Δ E_v为0.50 eV，这实际上等于没有插入层的GaAs/AlAs界面处的Δ E_v=0.51 eV。应变InAs单层膜的插入改变了GaAs/AlAs界面价电荷密度的细节，但不改变Δ Ev。计算结果与我们对MBE生长样品的实验测量结果一致。

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.