Controlled incorporation of the amphoteric dopant Si for n- and p-type conductivity in (Al,Ga)As epitaxial layers grown on (311)A-oriented GaAs substrates
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Beschreibung
In this work, the controlled incorporation of Si as a dopant in (Al,Ga)As(311)A and the inherent electrical properties of the layers are studied for a wide range of the aluminium mole fraction. The layers were grown by solid-source molecular beam epitaxy. Contrary to the (100)-orientation the amphoteric Si dopant incorporated via (311)A oriented surfaces enables n- and p-type conductivity. Main attention is paid to establishing growth conditions at which both n-type and p-type material can be prepared and a high Si doping efficiency is achieved. In particular for p-type doping, available work is limited to (Al,Ga)As layers with a low aluminium mole fraction. In this study, a substrate temperature range 460°C 0.6, a fixed Tg = 640°C and V/III BEP ratio = 5 were used. Capacitance-voltage (C-V) profiling, Hall-effect, and secondary ion mass spectrometry (SIMS) measurements have been carried out to characterize the Si incorporation. Optimized growth conditions were identified for achieving p-type doped AlxGa1-xAs with a doping efficiency above 80% in the full range of the alloy mole fraction, i.e. 0 ≤xAl ≤1. SIMS depth profiles for p-type AlxGa1-xAs/GaAs:Si layers, grown at Tg = 640°C with xAl > 0.6, show a long Si plateau, even at the AlxGa1-xAs/GaAs hetero-interface. This indicates a low diffusivity of Si, even at the high substrate temperature of 640°C. The electrical properties of Si delta-doped (Al,Ga)As(311)A layers are investigated in dependence of the growth parameters, in particular for doping of GaAs. As shown by C-V profiling, a spatial localization of the dopant within a few lattice constants and doping efficiencies above 90% were realized for n-type as well as for p-type delta-doped layers,
which were grown in a wide range of substrate temperatures, i.e. 480°C < Tg < 640°C.
The results of the doping studies were tested regarding their applicability for an (Al,Ga)As
based distributed Bragg reflector and successfully applied for a broad area laser.
Autor*in
Solomon Tibebu Kassa