Impact of the Ge-Si interfacial barrier on the temperature-dependent performance of PureGaB Ge-on-Si p ⁺n photodiodes

Area of Science:

• Optoelectronics
• Semiconductor Physics
• Materials Science

Background:

• Germanium-on-silicon (Ge-on-Si) photodiodes are crucial for near-infrared (NIR) applications.
• Understanding temperature-dependent performance is key for device reliability.
• Ge-on-Si heterointerfaces present unique challenges, including potential barriers.

Purpose of the Study:

• To investigate the temperature-dependent responsivity of Ge-on-Si photodiodes.
• To analyze the impact of the Ge-Si heterointerface barrier on photodiode performance.
• To evaluate the effectiveness of reverse bias in mitigating temperature-induced performance degradation.

Main Methods:

• Fabrication of n-Ge islands on n-Si substrates with specific capping layers (PureGaB).
• Temperature-dependent measurements of photodiode dark current and responsivity across a broad spectrum.
• Analysis of the Ge-Si heterointerface barrier and the effect of Al-migration during sidewall passivation.

Main Results:

• Ge-on-Si photodiodes exhibit low dark current and broadband responsivity.
• A potential barrier at the n-Ge/n-Si interface reduces responsivity at lower temperatures for wavelengths >1100 nm.
• Al-migration increases the barrier height but reverse bias application recovers room-temperature responsivity, significantly boosting performance at 1310 nm and 1550 nm.

Conclusions:

• The Ge-Si heterointerface barrier is a critical factor influencing Ge-on-Si photodiode responsivity.
• Reverse bias is an effective strategy to overcome temperature-dependent performance issues and enhance responsivity.
• Optimized sidewall passivation, including Al-migration, can reduce dark current and improve NIR detection capabilities.