  The short-wave infrared (SWIR) wavelength, especially 1.55 um, has attracted
significant attention in various areas such as high-speed optical communication
and LiDAR systems. Avalanche photodiodes (APDs) are a critical component as a
receiver in these systems due to their internal gain which enhances the system
performance. Silicon-based APDs are promising since they are CMOS compatible,
but they are limited in detecting 1.55 um light detection. This study proposes
a p-type Si on n-type GaAs0.51Sb0.49 (GaAsSb) lattice matched to InP substrates
heterojunction formed using a grafting technique for future GaAsSb/Si APD
technology. A p+Si nanomembrane is transferred onto the GaAsSb/AlInAs/InP
substrate, with an ultrathin ALD-Al2O3 oxide at the interface, which behaves as
both double-side passivation and quantum tunneling layers. The devices exhibit
excellent surface morphology and interface quality, confirmed by atomic force
microscope (AFM) and transmission electron microscope (TEM). Also, the
current-voltage (I-V) of the p+Si/n-GaAsSb heterojunction shows ideal
rectifying characteristics with an ideality factor of 1.15. The I-V tests
across multiple devices confirm high consistency and yield. Furthermore, the
X-ray photoelectron spectroscopy (XPS) measurement reveals that GaAsSb and Si
are found to have type-II band alignment with a conduction band offset of 50
meV which is favorable for the high-bandwidth APD application. The
demonstration of the GaAsSb/Si heterojunction highlights the potential to
advance current SWIR PD technologies.
