Micrometer-thick, atomically random Si0.06Ge0.90Sn0.04 for silicon-integrated infrared optoelectronics

TL;DR

This study demonstrates that a 1.5 μm-thick Si0.06Ge0.90Sn0.04 layer, nearly lattice-matched to Ge on Si, exhibits high crystalline quality, tunable infrared bandgap, and promising optoelectronic properties for silicon-integrated infrared photonics.

Contribution

We report the structural and optoelectronic properties of a nearly lattice-matched SiGeSn layer with direct bandgap absorption, advancing silicon-integrated infrared optoelectronics.

Findings

High crystalline quality and uniform composition of Si0.06Ge0.90Sn0.04 layer.

Direct bandgap absorption at 0.83 eV observed.

Photoconductive devices show responsivity similar to Ge on Si devices.

Abstract

A true monolithic infrared photonics platform is within reach if strain and bandgap energy can be independently engineered in SiGeSn semiconductors. Herein, we investigate the structural and optoelectronic properties of a 1.5 {\mu}m-thick Si0.06Ge0.90Sn0.04 layer that is nearly lattice-matched to a Ge on Si substrate. Atomic-level studies demonstrate high crystalline quality and uniform composition and show no sign of short-range ordering and clusters. Room temperature spectroscopic ellipsometry and transmission measurements show direct bandgap absorption at 0.83 eV and a reduced indirect bandgap absorption at lower energies. Si0.06Ge0.90Sn0.04 photoconductive devices operating at room temperature exhibit dark current and spectral responsivity (1 A/W below 1.5 {\mu}m wavelengths) similar to Ge on Si devices, with the advantage of a near-infrared band gap tunable by alloy composition. These results underline the relevance of SiGeSn semiconductors in implementing a group IV material platform for silicon-integrated infrared optoelectronics.