Optoelectronically Active GaAs/GeSn-MQW/Ge Heterojunctions Created via Semiconductor Grafting

TL;DR

This paper demonstrates a novel lattice-mismatched GaAs/GeSn-MQW/Ge heterojunction photodiode with record-low dark current and enhanced spectral response, enabled by advanced semiconductor grafting technology, expanding possibilities beyond traditional lattice-matched heterostructures.

Contribution

It introduces a new approach to create lattice-mismatched heterojunctions with superior performance using semiconductor grafting, surpassing limitations of conventional epitaxy.

Findings

Record-low dark current density of 1.22E-7 A/cm^2

Extended spectral response from 0.5 to 2 micrometers

Significant improvements in photoresponsivity in VIS and NIR ranges

Abstract

Traditionally, advancements in semiconductor devices have been driven by lattice-matched heterojunctions with tailored band alignments through heteroepitaxy techniques. However, there is significant interest in expanding the capabilities of heterojunction devices, in particular utilizing extreme lattice mismatches. We demonstrate the manipulation of device behaviors and performance enhancement achievable through a lattice-mismatched, single-crystalline GaAs/GeSn-multi-quantum well (MQW)/Ge n-i-p heterojunction by employing advanced semiconductor grafting technology. With engineered band alignment and optical field distribution, the grafted GaAs/GeSn-MQW/Ge n-i-p photodiode achieved outstanding performance: a record-low dark current density of 1.22E10^-7 A/cm^2, an extended spectral response from ~0.5 to 2 um, and improved photoresponsivity of RVIS of 0.85 A/W and RNIR of 0.40 A/W at 520 and 1570 nm, respectively. The dark current density is at least 5 orders of magnitude lower than state-of-the-art GeSn photodiodes. The photoresponsivity demonstrates an approximately sevenfold enhancement in the VIS range and a threefold improvement in the NIR range compared to the reference epitaxial photodiode. This work presents a unique strategy for constructing lattice-mismatched semiconductor heterojunction devices. More importantly, the implications transcend the current GaAs/GeSn-MQW/Ge example, offering potential applications in other material systems and freeing device design from the stringent lattice-matching constraints of conventional heteroepitaxy.