GaAs/AlGaAs Nanowire Photodetector (1601.02312v1)

Abstract: We demonstrate an efficient core-shell GaAs/AlGaAs nanowire photodetector operating at room temperature. The design of this nanoscale detector is based on a type-I heterostructure combined with a metal-semiconductor-metal (MSM) radial architecture, in which built-in electric fields at the semiconductor heterointerface and at the metal/semiconductor Schottky contact promote photogenerated charge separation, enhancing photosensitivity. The spectral photoconductive response shows that the nanowire supports resonant optical modes in the near-infrared region, which lead to large photocurrent density in agreement with the predictions of electromagnetic and transport computational models. The single nanowire photodetector shows remarkable peak photoresponsivity of 0.57 A/W, comparable to large-area planar GaAs photodetectors on the market, and a high detectivity of 7.2 10^10 cm\sqrt{Hz}/W at {\lambda}=855 nm. This is promising for the design of a new generation of highly sensitive single nanowire photodetectors by controlling optical mode confinement, bandgap, density of states, and electrode engineering.

• The paper demonstrates a GaAs/AlGaAs nanowire photodetector achieving a peak photoresponsivity of 0.57 A/W and a detectivity of 7.2×10⁹ cm Hz⁻¹/W at 855 nm.
• The paper employs a core-shell and MSM configuration that enhances light absorption and charge carrier separation for improved optoelectronic performance.
• The paper validates its findings using high-resolution TEM, photoluminescence, and simulations, illustrating a robust 2DET-like environment for next-generation nano-optoelectronic devices.

Overview of GaAs/AlGaAs Nanowire Photodetector

The paper presents a detailed investigation of a GaAs/AlGaAs core-shell nanowire photodetector that demonstrates significant efficiency improvements in optoelectronic performance at room temperature. The paper focuses on the synthesis and characterization of these nanostructures and highlights the advantageous role of their radial shell structure in enhancing light absorption and charge carrier separation. This novel photodetector harnesses a metal-semiconductor-metal (MSM) configuration, promoting significant potential for next-generation nano-optoelectronic devices.

This work takes advantage of the optical, electronic, and structural modalities provided by III-V semiconductor nanowires, which are known for superior control in heterostructure formation due to their high surface-area-to-volume ratio. The design utilizes a type-I heterostructure that enhances photoresponsivity and detectivity through strategic bandgap engineering and structural optimization. The core-shell configuration is instrumental in overcoming the drawbacks related to surface states that often impede nanowire photoconductors' efficacy. The inclusion of an aluminum gallium arsenide (AlGaAs) layer effectively passivates surface states, reducing recombination losses and enhancing carrier mobility.

Key Results

1. Photodetection Performance: The GaAs/AlGaAs nanowire photodetector achieves a peak photoresponsivity of 0.57 A/W, with a detectivity of 7.2 × 10⁹ cm Hz⁻¹/W at an operational wavelength of 855 nm. These performance metrics are comparable with commercially available large-area GaAs photodetectors.
2. Optical and Structural Properties: High-resolution transmission electron microscopy (HR-TEM) confirmed the quality of the crystalline zinc blende structure and demonstrated distinct layers between GaAs and AlGaAs regions. Simulations indicated high electron density accumulation at the heterointerface due to AlGaAs encapsulation, providing a two-dimensional electron tube (2DET)-like environment favorable for efficient photoinduced charge separation.
3. Spectral and Morphological Analyses: Photoluminescence and photocurrent measurements reveal that the AlGaAs shell plays a critical role in confining charge carriers and enhancing radiative recombination, evidenced by a significant emission peak shift. Furthermore, electromagnetic simulations revealed resonant optical modes within the GaAs core, contributing to enhanced light absorption and photodetection reliability.

Implications and Future Directions

The research elucidates the potential of engineered core-multishell nanowires in photodetection applications, particularly in telecommunication and imaging arrays where device miniaturization without performance compromise is desirable. Notably, the ability to maintain high efficiency at reduced sizes suggests applications in integrated photonic circuits, continuing the path towards more energy-efficient and compact optoelectronic devices.

The paper's implications extend towards a broader application scope, such as solar cells and optical interconnects, where high photoconversion efficiency and tailored wavelength sensitivity are critical. Future research could investigate further modulation of optical properties and increased integration with existing silicon-based technologies. Moreover, exploring other material combinations and expanding operational wavelengths may yield applications spanning broader spectrums and environments.

In conclusion, the work demonstrates a compelling advancement in nanowire photodetector technology, highlighting a concerted approach towards optimizing structural, optical, and transport properties for superior device performance. This lays a robust foundation for future explorations and applications in nanoscale optoelectronic systems.