Determination of Conduction Band Offsets in Type-II In0.27Ga0.73Sb/ InxAl1-xAsySb1-y Heterostructures Grown by Molecular Beam Epitaxy
NAVAL RESEARCH LAB WASHINGTON DC
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Low-temperature photoluminescence PL has been performed on a set of specially designed In0.27Ga0.73Sb InxAl1 xAsySb1 y multiple quantum well MQW heterostructures grown by molecular beam epitaxy in order to provide a measure of the conduction band offsets in this material system. These alloys are of interest for the development of high-speed heterojunction bipolar transistors HBTs that show promise for operation at lower power dissipation than in GaAs- and InP-based HBTs. Excitation power studies revealed evidence for strong electron-hole recombination at 0.56 eV within the InGaSb layers of the type-I MQW structure with x0.52, y0.25, while several weaker indirect transitions involving electrons in the InxAl1 xAsySb1 y and holes in the InGaSb layers were observed between 0.38 and 0.53 eV from the nominally type-II MQW samples with x, y0.67, 0390 and 0.69,0.41. Neglecting small corrections 15 meV due to the electron and hole confinement energies, we estimate conduction band offsets of 120 150 meV in these type-II structures. The general trends of the PL features as a function of excitation power have been reproduced from modeling of the quantum well electron and hole subband energies, including effects due to band bending at the heterointerfaces.
- Solid State Physics