Waveguide-coupled germanium (Ge) p-i-n photodetectors (PDs) have attracted much attention and have been investigated widely due to their high performance and enable on-chip integration. Conventional waveguide-coupled Ge PDs requires metal contact on Ge as well as doping in Ge to form the p-i-n junction. However, in these devices, the light absorption of metal contacts on Ge leads to a sharp decrease in responsivity. In addition, in the standard CMOS foundries, the technology of forming metal contact with Ge is immature. In this paper, we report on the design, fabrication, and experimental demonstration of an integrated lateral waveguide p-i-n photodetector (PD). We experimentally obtained at a reverse voltage of 3V a dark current of 11 nA, a responsivity higher than 0.73 A/W at 1550 nm wavelength, and a -3 dB opto-electrical cut-off frequency over 66 GHz. The combined benefits of decreased process complexity and high-performance device operation pave the way towards attractive integration strategies to deploy costeffective photonic transceivers on silicon-on-insulator substrates.
This paper proposes a GaN-based light-emitting diode based on an n-i-p terminal quantum barrier structure that is easy to implement in epitaxy, which can enhance electron confinement and improve hole injection efficiency. Existing GaNbased light-emitting diodes, due to the electron blocking layer (EBL) formed by inserting a wide band gap AlGaN material between the active region and the p-type hole injection layer, cannot effectively confine electrons, and also suppresses multiple quantum wells (MQWs) and Hole injection in the p-type region caused by the polarization field in the EBL. In order to improve the performance of GaN-based LEDs, better suppress electron leakage in the active region and increase the hole injection efficiency in the p-type region, a new design of the terminal quantum barrier was carried out, specifically n-GaN n-GaN (1×1018cm-3)-i-GaN-p-GaN (5×1018cm-3) terminal quantum barrier structure, the thickness of the n, i and p layers in the barrier structure are 4 nm, 5 nm and 4 nm, respectively. This paper uses simulation method to verify the terminal quantum barrier structure. The electrical and optical performance of the GaNbased MQW LED with conventional structure and the LED based on the n-i-p terminal quantum barrier structure were compared, including physical indicators such as output optical power, threshold voltage, and hole injection concentration. The simulation results show that, compared with the traditional structure, the LED with the nip terminal quantum barrier structure has higher output light power and lower threshold voltage, and significantly increases the hole concentration in the active area, which is more effective in suppressing Electronic leaks. The analysis results show that the strong reverse electrostatic field in the nip terminal quantum barrier structure can effectively enhance the electron confinement in the active region, suppress electron leakage and improve the p-type hole injection efficiency. In summary, it is shown that the nip terminal quantum barrier structure can be Effectively improve the performance of LEDs, showing better performance than conventional devices.
Waveguide-coupled germanium (Ge) p-i-n photodetectors (PDs) have attracted much attention and have been investigated widely due to their high performance and enable on-chip integration. In this paper, we report on the fabrication and experimental demonstration of an integrated lateral waveguide p-i-n PD with additional Si doping. In order to achieve a high performance detector, we used a novel silicon substrate doping to improve the electric field intensity in the active region. It is demonstrated by experiment that the strategy using additional Si doping to decrease dark current and to increase the bandwidth is more favorable. Using the additional Si doped p-i-n junction, the waveguide coupled Ge-on-Si p-i-n PD shows a comprehensive performance improvement. With comparison to the conventional waveguide coupled Ge-on-Si p-i-n PD, such a PD, owns an about 60% improvement on the tested -3 dB opto-electrical cut-off frequency and shows the smaller dark current at voltage of -1 V. We obtained at a reverse voltage of 1V a dark current lower than 30 nA, a responsivity higher than 1.1 A/W at 1550 nm wavelength, and a -3 dB optoelectrical cut-off frequency over 25 GHz. Evidently, the waveguide coupled Ge-on-Si p-i-n PD with additional p-i-n junction is very effective to promote the performance of device, which is very promising to be applied in the further high power Ge-on-Si PD fabrication.
Modeling and characteristic of the SMT Board Plug connector, which is used to connect micro optical transceiver to the main board, are proposed and analyzed in this paper. When the high speed signal transfers from the PCB of transceiver to main board through SMT Board Plug connector, the structure and material discontinuity of the connector causes insertion losses and impedance mismatches. This makes the performance of high speed digital system exacerbated. So it is essential to analyze the signal transfer characteristics of the connector and find out what factors affected the signal quality at the design stage of the digital system. To solve this problem, Ansoft's High Frequency Structure Simulator (HFSS), based on the finite element method, was employed to build accurate 3D models, analyze the effects of various structure parameters, and obtain the full-wave characteristics of the SMT Board Plug connectors in this paper. Then an equivalent circuit model was developed. The circuit parameters were extracted precisely in the frequency range of interests by using the curve fitting method in ADS software, and the result was in good agreement with HFSS simulations up to 8GHz with different structure parameters. At last, the measurement results of S-parameter and eye diagram were given and the S-parameters showed good coincidence between the measurement and HFSS simulation up to 4GHz.
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