SELECTIVELY SE-DOPED ALGAAS/GAAS HETEROSTRUCTURES WITH REDUCED DX-CENTER CONCENTRATIONS GROWN BY MOLECULAR-BEAM EPITAXY

We studied the DX centers in Se-doped Alx Ga1-xAs layers grown by molecular-beam epitaxy. The DX-center concentrations of these layers were considerably lower than in Si-doped layers because of their shallower DX-center energy levels. We also studied Se doping of AlGaAs layers, and applied Se doping to selectively doped AlGaAs/GaAs heterostructures to eliminate the influences of DX centers. By optimizing growth conditions, we obtained excellent two-dimensional electron gas characteristics comparable to those of conventional Si-doped heterostructures. Using Se-doped Al0.2 Ga0.8 As layers, we grew DX-center-free selectively doped AlGaAs/GaAs heterostructures having electron mobilities of 70 000 cm2 /V s at 77 K.