The outstanding performance and facile processability turn two-dimensional materials (2DMs) into the most sought-after class of semiconductors for optoelectronics applications. Yet, significant progress has been made toward the hybrid integration of these materials on silicon photonics (SiPh) platforms for a wide range of mid-infrared (MIR) applications. However, realizing 2D materials with a strong optical response in the NIR-MIR and excellent air stability is still a long-term goal. Here, we report a waveguide integrated photodetector based on a novel 2D GeP. This material uniquely combines narrow and wide tunable bandgap energies (0.51–1.68 eV), offering a broadband operation from visible to MIR spectral range. In a significant advantage over graphene devices, hybrid Si/GeP waveguide photodetectors work under bias with a low dark current of few nano-amps and demonstrate excellent stability and reproducibility. Additionally, 65 nm thick GeP devices integrated on silicon waveguides exhibit a remarkable photoresponsivity of 0.54 A/W and attain high external quantum efficiency of ∼ 51.3% under 1310 nm light and at room temperature. Furthermore, a measured absorption coefficient of 1.54 ± 0.3 dB/µm at 1310 nm suggests the potential of 2D GeP as an alternative infrared material with broad optical tunability and dynamic stability suitable for advanced optoelectronic integration.
Recent theoretical studies proposed that two-dimensional (2D) GaGeTe crystals have promising high detection sensitivity at infrared wavelengths and can offer ultra-fast operation. This can be attributed to their small optical bandgap and high carrier mobility. However, experimental studies on GaGeTe in the infrared region are lacking and this exciting property has not been explored yet. In this work, we demonstrate a short-wavelength infrared (SWIR) photodetector based on a multilayer (ML) GaGeTe field-effect transistor (FET). Fabricated devices show a p-type behavior at room temperature with a hole field-effect mobility of 8.6 - 20 cm2 V-1s-1. Notably, under 1310 nm illumination, the photo responsivities and noise equivalent power of the detectors with 65 nm flake thickness can reach up to 57 A/W and 0.1 nW/Hz1/2, respectively, at a drain-source bias (Vds) = 2 V. The frequency responses of the photodetectors were also measured with a 1310 nm intensity-modulated light. Devices exhibit a response up to 100 MHz with a 3dB cut-off frequency of 0.9 MHz. Furthermore, we also tested the dependence of the device frequency response on the applied bias and gate voltages. These early experimental findings stimulate the potential use of multilayer GaGeTe for highly sensitive and ultrafast photodetection applications.
Electrically tunable devices contribute significantly to key functions of photonics integrated circuits. Here, we demonstrate the tuning of the optical index of refraction based on hybrid integration of multilayered anisotropic GaGeTe on a silicon micro-ring resonator (Si-MRR). Under static applied (DC) bias and transverse-electric (TE) polarization, the device exhibits a linear resonance shift without any amplitude modulation. However, for the transverse-magnetic (TM) polarization, both amplitude and phase modulation is observed. The corresponding wavelength shift and half-wave voltage length product (𝑽 𝝅 . 𝒍) for the TE polarization are -1.78 pm/V and 0.9 V.cm, respectively.These values are enhanced for the TM polarizations and correspond to -6.65 pm/V and 0.28 V.cm, respectively. The dynamic radio frequency (RF) response of the devices was also tested at different bias conditions. Remarkably, the device exhibits a 1.6 MHz and 2.1 MHz response at 0 V and 7 V bias, respectively. Based on these findings, the integration of 2D GaGeTe on the silicon photonics platform has great potential for the next generation of integrated photonic applications such as switches and phase shifters.
Despite the wide applications of Short-Wave Infrared (SWIR) imaging, standard imaging materials require lattice matching and complex fabrication techniques which are relatively expensive. In this work, 50 nm thick amorphous indium telluride (In2Te3) films are RF sputtered on a silicon substrate at 300 C. The films are used to fabricate back-gated field-effect photodetectors (PDs). The In2Te3 detectors exhibit a broad wavelength response from 406 nm to 1600 nm and a photo responsivity of 0.44 AW -1 under 1310 nm excitation at 5 V bias. Furthermore, an n-type behavior with an electron field-effect mobility of 1.15 cm 2 V -1 s -1 is observed. We also evaluated the frequency response of the PDs under 1310 nm modulated light, a 3dB cut-off frequency of ~0.97 MHz is measured. Further, the device exhibits specific detectivity of the 1.32 x 10 9 Jones and very good stability at ambient conditions.
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