Investigation of heterogeneous integration of GaAsSb with GaP/Si for SWIR applications

Heterogeneous integration of III-V semiconductors on silicon (Si) allows for integrated photonics that respond to shorter wavelengths of light. The short-wave infrared (SWIR) wavelength of 1.55 μm is of special interest because it is a wavelength with low attenuation in optical fiber communication systems and has applications in LIDAR. Gallium Arsenide Antimonide (GaAsSb) has a bandgap that absorbs this wavelength. It also has a similar electron affinity to Si, making it an ideal candidate for integration into Si CMOS processes with a minimal conduction band offset.

The lattice constant mismatch of GaAsSb and Si poses a challenge for direct epitaxial growth of quality GaAsSb films. Additionally, heterogeneously integrating GaAsSb with Si using techniques like wafer bonding and epitaxial layer transfer often introduces oxide-related defects at the interface caused by both gallium and silicon based oxides. Some oxide is needed for the bonding process, but silicon dioxide acts as a major barrier due to its large bandgap in the GaAsSb-Si heterostructure. In this work, we investigate gallium phosphide (GaP) as an interface layer between GaAsSb and Si, which prevents the formation of silicon dioxide. To study the effect of the GaP interface layer, a separate absorption charge multiplication (SACM) avalanche photodiode (APD) with varied charge doping is modeled. Using GaP as a hole barrier for a unipolar barrier structure is also investigated. These simulations demonstrate that GaP acts as an incompatible interface layer between GaAsSb and Si for an SACM APD, but that GaP is suitable for a unipolar barrier structure.