The simulations of quasi one-dimensional (1D) and quasi three-dimensional (3D) device process and optoelectronic performance were conducted on silicon APD array pixels using Silvaco, realizing micro region analysis of the electric field distribution, avalanche gain, and photoelectric response characteristics of the APD photosensitive region. The multiplication coefficients corresponding to different positions of APD pixel were obtained and compared with the ideal 1D device structure. The results show that the multiplication factor of the center region of APD pixel is significantly higher than that of the edge of the photosensitive region. The simulation of microlens to converge the incident light to the center of the photosensitive region confirmed the increasement of APD avalanche multiplication current, i.e. the quasi 3D structural APD response is increased from 13.6 A/W to 54.8 A/W, and the effective fill factor is increased from 20.9% to 84.2%. Thus, the utilization rate of incident light is effectively improved.
Wideband detectors are becoming more and more widely used. In order to expand the response wavelength of silicon detectors, single-layer and double-layer antireflection coatings are used, and combined with the high gain characteristics of silicon avalanche photodetectors (APDs), their response band is extended to the range of 250-1100nm. Simulation analysis shows that the double layer antireflection coating has larger infrared enhancement than the single layer anti reflection coating. The Si APD with this structure can achieve high response from UV 250nm to 1100nm with multiplication, enabling efficient detection in the UV-visible-near-infrared band.
To meet the requirements of high dynamic range applications of LiDAR, this paper designs the silicon avalanche photodetector (Si APD) with large linear gain, which can reduce the difficulty of subsequent APD circuits and improve the accuracy of laser ranging. In this paper, a planar n+-p-π-p+ avalanche photodetector (APD) is formed by ion implantation and annealing process, based on a silicon intrinsic substrate wafer. And the device structure is optimized to improve the maximum gain value in linear mode. Based on this, a new trench with an ion implantation type guard ring is designed to enhance the linear gain range. The simulation results show that the device operates in the wavelength range of 400~1100 nm and reaches the peak response at 700 nm. The breakdown voltage is 153 V, and the dark current at 90% breakdown voltage is 1.47 nA. The gain range is 2~101 under 32~138 V bias, with a large gain dynamic range and good linearity of gain, which is beneficial for the subsequent amplification circuit. Meanwhile, the calculation shows that the input optical power of APD device corresponding to the optical current compression degree of -1 dB is -16 dBm, which has good linearity in the range of -70~-16 dBm, which is beneficial to improve the overall performance of LIDAR.
With the development of optoelectronic technology, InGaAs/InP avalanche photodiodes (APDs) are more and more used in fiber-optic communication systems with high bit rates and long-distance transmission because of their advantages of high sensitivity, low noise, and high speed. When etching mesa-type InGaAs/InP APDs, the edges of the mesa sidewalls are susceptible to premature breakdown due to the increased electric field, which affects the device's performance. In this paper, a shallow-etched mesa-type InGaAs/InP APD with a guard ring structure is proposed in order to suppress edge breakdown. By using Silvaco TCAD software for simulation, the results show that the structure proposed in this paper can limit the active region in the center region, effectively suppress the edge electric field, make the electric field distribution more uniform, and suppress the uncertainty of breakdowns, so that the reliability of the device is greatly increased. The final optimized device has a punch-through voltage of 16 V and a breakdown voltage of 41.3 V. The device has a diameter of 80 μm. The dark current is about 2.02 nA, and the gain is 36 when the breakdown voltage is 95%.
In this paper, we simulated and analyzed the effects of guard-ring’s depth and space on the performance of silicon avalanche photodetector (APD) based on the traditional n+-p-π-p+ structure. Two shallow trenches (ST) outside of the active region was used as the guard rings and the effects of depth and the spacing between the two ST on the performance of silicon APD arrays was simulated and analyzed. In order to optimize the parameters of the shallow trenches, we calculated the different characteristics of APD under different conditions, including the characteristics of APD such as breakdown voltage, multiplication factor, dark current, photocurrent and so on. The result shows the breakdown voltage and multiplication of APD become higher because of the shallow trench guard-rings and they are related to the PN junction depth.
In this paper, the direct bonding InGaAs/Si avalanche photodiode (APD) with certain gain is developed. This structure separates the optical absorption region (InGaAs) from the multiplication region (Si). Avalanche multiplication takes place in the Si layer after the carriers injected from the absorption region. InGaAs and Si wafer are connected together by wafer bonding technology. The interface quality of InGaAs / Si material is good through optimizing the physical and chemical cleaning methods and bonding conditions of InGaAs/InP and Si epitaxial wafers. The InGaAs / Si APD is fabricated by conventional semiconductor process. The gain of InGaAs / Si APD is 43 at 38V. Further optimization of the process can obtain lower dark current and higher gain bandwidth product. This kind of device can be used for long-distance optical fiber communication.
We demonstrate a bonding InSb/Si wafer and its application in APD. An InSb/Si APD with high gain and high bandwidth is discussed. Bonding wafer of InSb and Si is suitable to fabricate InSb/Si APD. The InSb/Si APD will have better performance than InSb APD, and it is suited for the detection in passive imaging and active imaging operation.
The high sensitivity APD arrays have more and more application in the data transmission, LIDAR, remote sensing, medical image diagnosis system, environmental monitoring, military reconnaissance and etc. A preliminary study of Si APD was carried out, including the simulation of the photoelectric characteristics of Si APD, the experiment of Si APD single chip and array, and the test of Si APD. The APD gain is above 100, dark current is several nA, the rise time is nanosecond level. The 4×4, 1×16 Si APD arrays with high gain, quick response and low dark current have been made by means of available conventional semiconductor technology. The pulse width of the transient response under 1064 nm pulse LD illuminated is less than 100 ns at 100 V bias voltage which the pulse width is limited by the following amplification circuit. Some measures to improve the responsivity of APD at 1064nm is discussed. The next step is to develop the CMOS compatible high sensitivity APD array integrated with CMOS readout circuit.
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