A HIGH-GAIN, MODULATION-DOPED PHOTODETECTOR USING LOW-TEMPERATURE MBE-GROWN GAAS

In this letter, we report the fabrication and performance of a novel, high gain photodetector. Basically, the device is a modulation-doped f ield effect transistor (MODFET) structure with its channel region made of low-temperature MBE-grown GaAs. It exhibits an excellent responsiv ity of 65 A/W at similar to 0.87 mu m and 6.5 A/W at similar to 1.0 mu m. In the sub-bandgap range (0.9-1.3 mu m) the responsivity of this d evice is the highest ever reported, to our knowledge, for any GaAs-bas ed device. Thus, the device appears to be ideally suited for applicati ons requiring a high photodetection sensitivity, especially in the 1.3 mu m wavelength region. Charge separation by the built-in field norma l to the heterojunction plane is attributed to be responsible for the gain in the device.