Determination of conduction band offsets in type-Ⅱ In_(0.27)Ga_(0.73)Sb/In_xAl_(1-x)As_ySb_(1-y) heterostructures grown by molecular beam epitaxy

摘要

Low-temperature photoluminescence (PL) has been performed on a set of specially designed In_(0.27)Ga_(0.73)Sb/In_xAl_(1-x)As_ySb_(1-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 (x = 0.52, y = 0.25), while several weaker indirect transitions involving electrons in the In_xAl_(1-x)As_ySb_(1-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, y) = (0.67, 0.39) 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.