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Avalanche photodetectors (APDs) on Si operating at optical communication wavelength band are crucial for Si-based transceiver application. In this paper, we report the first O-band InAs quantum dot (QD) waveguide avalanche photodetectors monolithically grown on Si with a low dark current of 0.1 nA at unit gain and a responsivity of 0.234 A/W at 1.310 μm at unit gain (-5V). In the linear gain mode, the APDs have a maximum gain of 198 and show a clear eye diagram up to 8 Gbit/s. These QD-based APDs enjoy the benefit of sharing the same epitaxial layers and processing flow as QD lasers, which could potentially facilitate the integration with laser sources on Si platform.

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High speed mid-wave infrared (MWIR) photodetectors have important applications in the emerging areas such highprecision frequency comb spectroscopy and light detection and ranging (LIDAR). In this work, we report a high-speed room-temperature mid-wave infrared interband cascade photodetector (ICIP) based on a type-II InAs/GaSb superlattice. The devices show an optical cut-off wavelength around 5µm and a 3-dB bandwidth up to 7.04 GHz. The relatively low dark current density around 9.39 × 10 −2 A/cm 2 under −0.1 V is also demonstrated at 300K. These results validate the advantages of ICIPs to achieve both high-frequency operation and low noise at room temperature. Limitations on the high-speed performance of the detector are also discussed based on the S-parameter analysis and other RF performance measurement.Semiconductor photodetectors sensitive to mid-wave infrared (MWIR) have attracted extensive attentions in many applications such as chemical sensing, gas monitoring and high-performance infrared imaging. In some special applications, such as free-space optical communication and frequency comb spectroscopy, MWIR photodetectors capable of highfrequency operation are required as an essential component 1-6 . Currently, quantum well infrared photodetectors (QWIPs) and quantum cascade photodetectors (QCDs) for high speed MWIR applications have been demonstrated [7][8][9] . Nevertheless performance of QCDs is mainly limited by absorption efficiency and noise due to a short carrier lifetime 10-15 , and QWIPs have shortcomings in large dark currents and no response to normal incident light 7,16 .Compared with conventional photodetectors, interband cascade infrared photodetectors (ICIPs) have more flexibility to alleviate the limitation on absorber thickness due to a finite diffusion length so that all photo-generated carriers can be efficiently collected, while absorption of incident light can be ensured with multiple absorbers located in each stage connected in series 16 . On the other hand, the individual absorber thickness in every stage can be shortened to reduce the carrier transit time across a single stage. Another advantage of ICIPs is that noise is suppressed by the multiple discrete short absorbers, instead of a single long absorber 17,18 . As one of the most widely studied material system for MWIR, ICIPs based on InAs/GaSb type-II superlattice (T2SL) could offer several advantages such as wavelength tunability between 1 to 25 μm, excellent carrier transport properties and signal to noise ratio (SNR) 16 . Lotfi et al. reported a three-stage ICIP based on InAs/GaSb/AlSb/InSb T2SLs with a cutoff wavelength around 4.2µm at 300K, and the corresponding 3-dB bandwidth was ~1.3 GHz under zero bias 19 . Recently, a two-stage ICIP employing the InAs/Ga(As)Sb T2SLs as the absorption layer with cutoff wavelength of 5.6 μm and the 3-dB bandwidth of 2.4 GHz under −5 V bias at 300 K was demonstrated by our group 20 . In this paper, we report a five-stage ICIP based on InAs/GaSb type-II superlattice with a thin absorber of ...

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