Is grown on GaAs

PHYSICS · Multi-part · Fermi University Physics · Condensed Matter, Materials & Soft Matter · Semiconductor physics and devices · Semiconductor physics and devices

Solid State Physics, Ch Heterostructures, quantum wells and the two-dimensional electron gas

Problem

\mathrm{Al_{0.35}Ga_{0.65}As}

is grown on GaAs. At

300\,\mathrm{K}

E_g(\mathrm{GaAs})=1.424\,\mathrm{eV}

and

E_g(\mathrm{Al_xGa_{1-x}As})=1.424+1.247x\,\mathrm{eV}

. The measured band-offset split of the gap difference for this alloy system is 65 per cent to the conduction band and 35 per cent to the valence band. ((a)) Find

\Delta E_C

and

\Delta E_V

at the interface. ((b)) State, with a one-sentence reason, whether this is a type-I or type-II alignment, and say which layer confines both electrons and holes. ((c)) The GaAs is now doped p-type and the AlGaAs n-type. Describe in words how the band edges move on approaching the interface from each side, and what forms on each side of the junction, using the equilibrium picture built for a doped junction.

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