In this work, a two-step metal organic chemical vapor deposition (MOCVD) method was applied for growing β-Ga₂O₃ film on c-plane sapphire. Optimized buffer layer growth temperature (T_B) was found at 700 °C and the β-Ga₂O₃ film with full width at half maximum (FWHM) of 0.66° was achieved. A metal?semiconductor?metal (MSM) solar-blind photodetector (PD) was fabricated based on the β-Ga₂O₃ film. Ultrahigh responsivity of 1422 A/W @ 254 nm and photo-to-dark current ratio (PDCR) of 10⁶ at 10 V bias were obtained. The detectivity of 2.5 × 10¹⁵ Jones proved that the photodetector has outstanding performance in detecting weak signals. Moreover, the photodetector exhibited superior wavelength selectivity with rejection ratio (R_{250 nm}/R_{400 nm}) of 10⁵. These results indicate that the two-step method is a promising approach for preparation of high-quality β-Ga₂O₃ films for high-performance solar-blind photodetectors.

Expanding the optical communication band is one of the most effective methods of overcoming the nonlinear Shannon capacity limit of single fiber. In this study, GeSn resonance cavity enhanced (RCE) photodetectors (PDs) with an active layer Sn component of 9%–10.8% were designed and fabricated on an SOI substrate. The GeSn RCE PDs present a responsivity of 0.49 A/W at 2 μm and a 3-dB bandwidth of approximately 40 GHz at 2 μm. Consequently, Si-based 2 μm band optical communication with a transmission rate of 50 Gbps was demonstrated by using a GeSn RCE detector. This work demonstrates the considerable potential of the Si-based 2 μm band photonics in future high-speed and high-capacity optical communication.

High-performance germanium (Ge) waveguide photodetectors are designed and fabricated utilizing the inductive-gain-peaking technique. With the appropriate integrated inductors, the 3-dB bandwidth of photodetectors is significantly improved owing to the inductive-gain-peaking effect without any compromises to the dark current and optical responsivity. Measured 3-dB bandwidth up to 75 GHz is realized and clear open eye diagrams at 64 Gbps are observed. In this work, the relationship between the frequency response and large signal transmission characteristics on the integrated inductors of Ge waveguide photodetectors is investigated, which indicates the high-speed performance of photodetectors using the inductive-gain-peaking technique.High-performance germanium (Ge) waveguide photodetectors are designed and fabricated utilizing the inductive-gain-peaking technique. With the appropriate integrated inductors, the 3-dB bandwidth of photodetectors is significantly improved owing to the inductive-gain-peaking effect without any compromises to the dark current and optical responsivity. Measured 3-dB bandwidth up to 75 GHz is realized and clear open eye diagrams at 64 Gbps are observed. In this work, the relationship between the frequency response and large signal transmission characteristics on the integrated inductors of Ge waveguide photodetectors is investigated, which indicates the high-speed performance of photodetectors using the inductive-gain-peaking technique.

Beta-gallium oxide (β-Ga₂O₃) thin films were deposited onc-plane (0001) sapphire substrates with different mis-cut angles along < 112ˉ0> by metal-organic chemical vapor deposition (MOCVD). The structural properties and surface morphology of as-grownβ-Ga₂O₃ thin films were investigated in detail. It was found that by using thin buffer layer and mis-cut substrate technology, the full width at half maximum (FWHM) of the ( 2ˉ01) diffraction peak of theβ-Ga₂O₃ film is decreased from 2° onc-plane (0001) Al₂O₃ substrate to 0.64° on an 8° off-angledc-plane (0001) Al₂O₃ substrate. The surface root-mean-square (RMS) roughness can also be improved greatly and the value is 1.27 nm for 8° off-angledc-plane (0001) Al₂O₃ substrate. Room temperature photoluminescence (PL) was observed, which was attributed to the self-trapped excitons formed by oxygen and gallium vacancies in the film. The ultraviolet–blue PL intensity related with oxygen and gallium vacancies is decreased with the increasing mis-cut angle, which is in agreement with the improved crystal quality measured by high resolution X-ray diffraction (HR-XRD). The present results provide a route for growing high qualityβ-Ga₂O₃ film on Al₂O₃ substrate.Beta-gallium oxide (β-Ga₂O₃) thin films were deposited onc-plane (0001) sapphire substrates with different mis-cut angles along < 112ˉ0> by metal-organic chemical vapor deposition (MOCVD). The structural properties and surface morphology of as-grownβ-Ga₂O₃ thin films were investigated in detail. It was found that by using thin buffer layer and mis-cut substrate technology, the full width at half maximum (FWHM) of the ( 2ˉ01) diffraction peak of theβ-Ga₂O₃ film is decreased from 2° onc-plane (0001) Al₂O₃ substrate to 0.64° on an 8° off-angledc-plane (0001) Al₂O₃ substrate. The surface root-mean-square (RMS) roughness can also be improved greatly and the value is 1.27 nm for 8° off-angledc-plane (0001) Al₂O₃ substrate. Room temperature photoluminescence (PL) was observed, which was attributed to the self-trapped excitons formed by oxygen and gallium vacancies in the film. The ultraviolet–blue PL intensity related with oxygen and gallium vacancies is decreased with the increasing mis-cut angle, which is in agreement with the improved crystal quality measured by high resolution X-ray diffraction (HR-XRD). The present results provide a route for growing high qualityβ-Ga₂O₃ film on Al₂O₃ substrate.

Abstract

GeSn detectors have attracted a lot of attention for mid-infrared Si photonics, due to their compatibility with Si complementary metal oxide semiconductor technology. The GeSn bandgap can be affected by Sn composition and strain, which determines the working wavelength range of detectors. Applying the Sn content gradient GeSn layer structure, the strain of GeSn can be controlled from fully strained to completely relaxed. In this work, the strain evolution of GeSn alloys was investigated, and the effectiveness of gradually increasing Sn composition for the growth of high-Sn-content GeSn alloys was revealed. Relaxed GeSn thick films with Sn composition up to 16.3% were grown, and GeSn photodetectors were fabricated. At 77 K, the photodetectors showed a cutoff wavelength up to 4.2 μm and a peak responsivity of 0.35 A/W under 1 V at 2.53 μm. These results indicate that GeSn alloys grown on a Sn content gradient GeSn structure have promising application in mid-infrared detection.

硅材料在1.1~8.5 μm有非常低的吸收损耗，因此硅基光电子学有望扩展到中红外波段。并且随着通信窗口扩展、气体分子检测、红外成像等应用需求的出现，硅基中红外波段器件研发工作的开展势在必行。在中红外波段硅基光电子器件中，硅基调制器有着举足轻重的地位：它是长波光通信链路中不可或缺的一环，还可以应用在片上传感系统中提高信噪比、实现光开关等功能。研究发现，相比于近红外波段，硅和锗材料在中红外波段有更强的自由载流子效应和热光效应，因此，基于硅基材料的中红外调制器具有独天得厚的优势。系统总结了中红外硅基调制器的发展趋势和研究现状，介绍了基于硅和锗材料的电光调制器以及热光调制器的工作原理和最新研究进展，最后对中红外硅基调制器进行了总结与展望。

硅基IV族锗锡和锗铅合金材料带隙随组分可调，并可转变成直接带隙半导体材料，是研制硅基红外探测和发光器件的理想材料。本文首先介绍锗锡和锗铅材料外延生长工作，然后对锗锡光电器件的研究进展进行回顾和讨论。其中，随着锗锡合金中锡组分增加，锗锡光电探测器往高响应度和长探测截止波长方向发展；锗锡激光器的研究则集中在降低激射阈值、提高激射温度和电泵浦方面。本文还对锗铅材料和光电器件的研究进展进行简要介绍和展望。随着硅基高效光源和探测器研究的不断深入，IV族合金材料在硅基红外光电集成领域将继续展现重要的应用价值。

We report the demonstration of a normal-incidence p-i-n germanium-tin (Ge0.951Sn0.049) photodetector on silicon-on-insulator substrate for 2 μm wavelength application. The DC and RF characteristics of the devices have been characterized. A dark current density under -1V bias of approximately 125mA/cm2 is achieved at room temperature, and the optical responsivity of 14 mA/W is realized for illumination wavelength of 2 μm under -1V reverse bias. In addition, a 3 dB bandwidth (f3dB) of around 30 GHz is achieved at -3V, which is the highest reported value among all group III–V and group IV photodetectors working in the 2 μm wavelength range. This work illustrates that a GeSn photodetector has great prospects in 2 μm wavelength optical communication.