SELENIUM AND SILICON DELTA-DOPING PROPERTIES OF GAAS BY ATMOSPHERIC-PRESSURE METALORGANIC CHEMICAL VAPOR-DEPOSITION

We investigate selenium and silicon delta-doping characteristics for GaAs layers grown by atmospheric pressure metalorganic chemical vapor deposition. Broadened capacitance-voltage (C-V) profiles and low doping activities are found in case of Se delta doping. In contrast, excellent delta-doping characteristics result for silicon. The obtained C-V full width at half maximum are in the range of 44-49 Å for samples even with substrate temperatures of 700-750 °C, which are relatively high compared with the molecular-beam epitaxy (MBE) substrate temperature. Hall mobility measurements show the mobility enhancement due to a screening of impurity charges. Also, Shubnikov-de Haas oscillations demonstrate the two-dimensional nature of electrons confined in the delta-doped layers. Therefore, our delta-doped layers show no substantial differences in quality with MBE-grown delta-doped layers. In addition, preliminary delta field-effect transistors having a gate length of 1.5 μm and a gate width of 300 μm are fabricated.