Hamamatsu Photonics has introduced APDs (avalanche photodiodes) that are claimed to offer enhanced near-infra red sensitivity. Using laser processing technology, MEMS structures can be fabricated on the silicon surface which act to reduce reflections and increase the surface area of the active element. This process is claimed to increase the sensitivity in wavelengths longer than 800nm. The S11518 and S11519 are silicon APDs using this technology, offering sensitivities at 1000nm, of between 70 and 75A/W at a gain of 100. According to the company, compared to conventional APDs designed for YAG (yttrium aluminium garnet) laser detection, these offer an additional 15 to 20A/W photo sensitivity, under the same operating conditions. The increased sensitivity in the near-infra red region makes the IR-enhanced APD suitable for YAG laser monitors, and IR measurements. At 1.06µm, the quantum efficiency of the APDs reaches 40%, compared to 20% for a conventional APD, claims the company. Both APDs are available in one and 3mm diameter active area types, which offer bandwidths between 220 and 400MHz. The S11519 is designed for low bias operation, with enhanced breakdown voltage, dark current and cut-off frequency characteristics.
