The rapid advancement of large-scale artificial intelligence (AI) models has driven exponential growth in the demand for computing power and data capacity. To date, China has established the world’s largest and most advanced fiber-optic and mobile communication networks. The data center industry in China has maintained an average annual growth rate of 30% over the past five years. As the backbone of global telecommunications infrastructure, optical communication systems now face unprecedented challenges in handling massive data transmission. Transmission rates have advanced from 45 Mbit/s in the first generation to 400 Gbit/s in the fifth generation, with a target capacity of 10 Tbit/s. To meet the evolving demands of high-speed optical communication systems, there is an urgent need to develop next-generation high-speed photodetectors that meet new technical standards. These devices must achieve a response bandwidth exceeding 57 GHz in single-wavelength 100 Gbit/s optical channels while maintaining a responsivity above 0.5 A/W. Based on this, we propose an avalanche uni-traveling carrier photodetector with an electric field regulation layer (ER-AUTC-PD). This innovative structure significantly enhances photodetector responsivity while preserving high-speed response characteristics.

In this paper, we focus on the device structure design and performance optimization of the proposed ER-AUTC-PD, employing the Silvaco ATLAS semiconductor device simulation tool (TCAD) for modeling. An intrinsic InP multiplication layer is introduced between the cliff layer and the absorption layer to achieve photocurrent avalanche gain via impact ionization. In addition, a p-InP electric field regulation layer is inserted between the collection layer and the cliff layer. By co-optimizing the doping concentrations of both the cliff layer and the electric field regulation layer, the high-electric-field region is localized in the InP multiplication layer to enhance avalanche gain, while the electric field within the collection layer is tuned to approach the field intensity corresponding to the electron peak drift velocity, thus improving high-speed response characteristics. Subsequently, the thickness of the collection layer is optimized. The increased electron transport speed partially compensates for the delay caused by the longer transit distance in the thicker collection layer, helping to reduce parasitic capacitance and further enhancing high-speed performance. Moreover, the interrelationships and trade-offs among photocurrent gain, bias voltage, electron transport properties, and parasitic capacitance are comprehensively analyzed to achieve balanced performance. The final ER-AUTC-PD structure is thus designed.

The proposed ER-AUTC-PD demonstrates improved gain-bandwidth product performance compared to traditional APDs, achieving a gain-bandwidth product of up to 360 GHz [Fig. 6(a)]. The device also exhibits excellent responsivity and high-speed optical response. Under a bias voltage of -10.1 V, a 14 μm-diameter device achieves a 3 dB bandwidth of 63 GHz, a responsivity of 0.501 A/W, and a multiplication gain (M) of 2.34. Under a -10.4 V bias, a 10 μm-diameter device reaches a 3 dB bandwidth of 75 GHz with a responsivity of 0.505 A/W and M=2.44 [Fig. 6(b)]. With an incident optical power of 15.4 μW and a responsivity of 0.5 A/W, the optimized ER-AUTC-PD achieves a 3 dB bandwidth of 63 GHz, significantly outperforming the 43 GHz bandwidth of a pre-optimized MUTC-PD, clearly demonstrating the benefits of structural optimization [Fig. 7(b)]. Furthermore, comparison with several reported APDs (Table 2) shows that the ER-AUTC-PD offers superior performance in terms of low power consumption, high responsivity, and high bandwidth.

In this paper, we propose an avalanche uni-traveling carrier photodetector with an electric field regulation layer. By introducing a multiplication layer between the absorption layer and the cliff layer, photo-generated electrons undergo impact ionization under a strong electric field to achieve avalanche gain. A p-InP electric field regulation layer is also added between the collection layer and the cliff layer. Through coordinated optimization of the doping concentrations in the cliff and electric field regulation layers, the electric field is precisely distributed to localize the high-field-intensity region within the multiplication layer and maintain a field strength corresponding to the electron peak drift velocity in the collection layer. This configuration enables both enhanced responsivity and improved 3 dB bandwidth. Furthermore, the trade-offs among photocurrent gain, bias voltage, electron transport behavior, and parasitic capacitance are analyzed to reach an optimal balance. The optimized 14 μm-diameter device achieves a 3 dB bandwidth of 63 GHz under a -10.1 V bias, with a responsivity of 0.501 A/W and an M of 2.34. The 10 μm-diameter version reaches a 3 dB bandwidth of 75 GHz at -10.4 V, with 0.505 A/W responsivity and an M of 2.44. The ER-AUTC-PD shows clear performance advantages in two key areas: first, it achieves a higher gain-bandwidth product than traditional APDs; second, it significantly reduces power consumption by operating at a lower avalanche reverse bias voltage. These results demonstrate that the ER-AUTC-PD provides excellent performance in low power consumption, high responsivity, and high bandwidth, meeting the requirements for single-wavelength 100 Gbit/s optical communication systems.