Low temperature Al2O3 surface passivation for carrier-injection SiGe optical modulator

Area of Science:

• Materials Science
• Semiconductor Physics
• Optical Engineering

Background:

• Surface recombination in silicon-germanium (SiGe) optical modulators limits device performance.
• Effective surface passivation is crucial for improving carrier-injection SiGe optical modulator efficiency.
• Low-temperature deposition methods are desirable for SiGe device fabrication.

Purpose of the Study:

• To investigate the efficacy of aluminum oxide (Al2O3) passivation deposited by atomic layer deposition (ALD) at 200 °C for SiGe optical modulators.
• To compare the interface trap densities of Al2O3/Si and silicon dioxide (SiO2)/Si interfaces.
• To evaluate the impact of Al2O3 passivation on the modulation efficiency of SiGe optical modulators.

Main Methods:

• Surface passivation using Al2O3 deposited by ALD at 200 °C.
• Investigation of interface trap densities at SiO2/Si and Al2O3/Si interfaces.
• Fabrication and characterization of metal-oxide-semiconductor (MOS) capacitors.
• Evaluation of modulation efficiency in SiGe optical modulators.

Main Results:

• Al2O3 passivation resulted in an interface trap density over an order of magnitude lower than SiO2 passivation.
• Inserting an Al2O3 layer before SiO2 deposition by plasma-enhanced chemical vapor deposition (PECVD) improved modulation efficiency by 1.3 times.
• Al2O3 passivated devices showed modulation efficiency comparable to those passivated with thermally grown SiO2.
• ALD Al2O3 passivation is effective for low-temperature processing of SiGe optical modulators.

Conclusions:

• ALD Al2O3 is a highly effective surface passivation technique for SiGe optical modulators.
• The superior interface quality achieved with ALD Al2O3 significantly enhances device performance.
• This low-temperature passivation method is suitable for fabricating high-efficiency SiGe optical modulators.