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 (nₛᵉ) in the quantum well of a symmetric GaAs-Alₓ{Ga}_{1{{-}}x}$As-${In}yGa_1-yAs-Alₓ{Ga}_{1{{-}}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 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 {~}10¹¹ cm^-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.