Impact of arsenic species on InAs/GaSb type II superlattice grown by molecular beam epitaxy

In this study, InAs/GaSb type-II superlattice (T2SL) structures were grown on GaSb substrates by molecular beam epitaxy to investigate the impact of arsenic species (As2 dimers vs As4 tetramers) and growth temperatures (385–425 °C) on the interface quality and device performance. Structural characterization revealed that InAs layers grown with As4 at 385 °C exhibit superior crystallinity, evidenced by sharper higher-order satellite peaks and minimal lattice strain in high-resolution x-ray diffraction patterns. High-resolution transmission electron microscopy further confirms the abruptness of the interface with suppressed intermixing. Photoluminescence measurements demonstrate enhanced emission intensity and narrower linewidths for samples grown with As4 at 385 °C compared to those grown with As2. The reduced reactivity and sticking coefficient of As4, relative to As2, likely suppress uncontrolled anion exchange, particularly at lower growth temperatures. In contrast, As2 facilitates direct substitutional incorporation, driven by lower activation energy barriers, which promotes aggressive As-Sb exchange at heterointerfaces. This leads to compromised crystal integrity through the formation of parasitic ternary/quaternary phases and an increase in nonradiative defect centers, which adversely affect optical performance. Fabricated p-i-n diodes utilizing the optimized As4-grown T2SL exhibit a low room-temperature dark current density of 2.2 × 10−5 A/cm2, attributed to the suppression of generation-recombination and tunneling currents via enhanced interface quality. These results demonstrate that As4-mediated growth effectively mitigates anion exchange, paving the way for high-operating-temperature T2SL devices in midwave infrared optoelectronics.