SE-DOPED ALGAAS GROWN ON GAAS(111)A BY MOLECULAR-BEAM EPITAXY

The electrical properties of Se-doped Al0.3Ga0.7As layers grown by molecular beam epitaxy (MBE) on GaAs(111)A substrates have been investigated by Hall-effect and deep level transient spectroscopy (DLTS) measurements. In Se-doped GaAs layers, the carrier concentration depends on the misorientation angle of the substrates; it decreases drastically on the exact (111)A surface due to the re-evaporation of Se atoms. By contrast, in Se-doped AlGaAs layers, the decrease is not observed even on exact oriented (111)A. This is caused by the suppression of the re-evaporation of Se atoms, by Se-Al bonds formed during the Se-doped AlGaAs growth. An AlGaAs/GaAs high electron mobility transistor (HEMT) structure has been grown. The Hall mobility of the sample on a (111)A 5 degrees off substrate is 5.9 X 10(4) cm(2)/V . s at 77 K. This result shows that using Se as the n-type dopant is effective in fabricating devices on GaAs(111)A.