SiGe Nanomembrane Quantum-Well Infrared Photodetectors

SiGe quantum wells are promising candidates for the development of intersubband light emitters and photo detectors operating at mid- and far-infrared wavelengths. By virtue of their inherent compatibility with the Si microelectronics platform, these devices may be integrated seamlessly within complex optoelectronic systems for sensing and imaging applications. However, the development of high-quality SiGe intersubband active layers is complicated by the large lattice mismatch between Si and Ge, which limits the number of quantum wells that can be grown on bulk Si substrates before the onset of structural degradation due to inelastic strain relaxation. To address this issue, we investigate the use of lattice matched growth templates consisting of quantum-well nanomembrane stacks that were at one point free-standing, allowing for the internal stress to be relaxed via elastic strain sharing rather than defect formation. SiGe quantum-well infrared photodetectors (QWIPs) based on this approach are developed and characterized. Efficient current extraction from these ultrathin devices is obtained by bonding the nanomembranes directly on a doped Si substrate. Pronounced photocurrent peaks at mid-infrared wavelengths are measured, with improved responsivity compared to otherwise identical devices grown simultaneously on the supporting Si substrate.