Optical spectroscopy of a double-barrier resonant-tunneling structure containing a narrow-gap, strained-layer, quantum-well region

Photoluminescence excitation (PLE) and photoluminescence (PL) spectroscopies are employed to study the charge buildup (${\mathit{n}}_{\mathit{s}}^{\mathit{e}}$) in the quantum well of a symmetric GaAs-${\mathrm{Al}}_{\mathit{x}}$${\mathrm{Ga}}_{1\mathrm{-}\mathit{x}}$As-${\mathrm{In}}_{\mathit{y}}$${\mathrm{Ga}}_{1\mathrm{-}\mathit{y}}$As-${\mathrm{Al}}_{\mathit{x}}$${\mathrm{Ga}}_{1\mathrm{-}\mathit{x}}$As-GaAs (x=0.33, y=0.09) double-barrier resonant-tunneling structure. The use of a narrower-gap indium-containing quantum-well region allows PLE to be employed without the spectroscopic interference from the ${\mathit{n}}^{+}$-type GaAs contact regions which occurs in conventional double-barrier structures. The structures are shown to be on resonance at zero applied bias (V=0), with electron densities in the well at V=0 of ∼${10}^{11}$ ${\mathrm{cm}}^{\mathrm{-}2}$ due to the charge transfer required to establish equilibrium. The form of the I-V characteristics at the first resonance close to V=0 is explained on the basis of tunneling from electron states in the three-dimensional contacts into the two-dimensional quantum-well level. The contribution of extrinsic processes to the PL spectra is discussed.