InGaAsP/InP wavelength-selective heterojunction phototransistors


High-gain phototransistors with narrow spectral response (wavelength-selective phototransistors) have been developed by adding an absorption layer to a wide-bandgap heterojunction phototransistor using the InGaAsP/InP material system. The spectral response peaks at approximately 1.2 µm and the spectral half-width of 53 nm is achieved. This device exhibited an optical gain as high as 400 at the peak wavelength under an incident light power P<inf>in</inf>of 3.6 µW. The rise time was measured to be 18 µs at P<inf>in</inf>= 10 µW. The noise characteristic was also measured for this device, and the resultant detectivity D<sup>*</sup>was estimated to be 3.7 × 10<sup>10</sup>cm . Hz<sup>1/2</sup>/W at a frequency of 2 kHz under an optical bias level of 0.1 µW. These characteristics have been theoretically discussed in detail.


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