| 摘要 |
A photodetector has an extended wavelength range combined with high responsivity and reliability. It includes an active region having alternating compressive and tensile strain layers arranged so that the total effective strain of the active region is balanced. The thickness of each layer is limited so that a product of a thickness by strain is not exceeding about 20%nm to avoid formation of crystalline defects. The layers with higher optical absorption constant are made thicker than the layers with lower absorption constant to provide the required responsivity of the detector. In one embodiment, the active region is formed on InP substrate and includes alternating 0.25% compressive strain and 1.03% tensile strain layers of InGaAs composition, the compressive strain layers being approximately four times thicker. In another embodiment interfaces between the layers are compositionally graded. The described structure of the active region may be used in various types of photodetectors, e.g., PIN, APD, MSM, Shottky barrier and waveguide photodetectors. Depending on the materials used, the photodetector is capable of operating in a wide wavelength range, e.g. up to 2200 nm, and covering a wide range of temperatures, including cryogenic temperatures.
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