Band offsets of $AlxGa1−xSbAs/InGaAs$ heterojunctions

By applying van de Walle and Martin’s model solid theory (MST), we have investigated the compositional dependence of the band-edge alignment at the $AlxGa1−xSbAs/InGaAs$ and $AlxGa1−xSbAs/InAlAs$ heterointerfaces lattice-matched to InP. A comparison between theoretical calculations and previously published experimental values on ternary extremes of $AlxGa1−xSbAs$ yields a discrepancy of 0.1–0.2 eV for GaSbAs/InAlAs and GaSbAs/InGaAs, and 0.3 eV for AlSbAs/InAlAs and AlSbAs/InGaAs. For all four heterostructures, it has been found that the MST results shift the valence band edge of the (Sb, As) alloy downward relative to that of InAlAs and InGaAs as compared to experimental data, and possible causes of the disagreement are analyzed. Furthermore, the band offset values have been obtained from a current–voltage measurement on $InGaAs/AlxGa1−xSbAs/InGaAs$ semiconductor–insulator–semiconductor diodes. The carrier transport mechanism in these diodes is discussed and the measured offset values are shown to be in qualitative agreement with the MST predictions.