Fig. 3.
Influence of the gate voltage on the photodetector performance in the infrared regime. a Responsivity of the fabricated photodetector at wavelengths ranging from 3 to 20 μm. Inset figures illustrate intraband transitions at wavelengths of 3 and 20 μm under gate voltages of −20 and 65 V. The measured responsivity values show errors as large as ±20% because of thermal fluctuations in the measurement environment that lead to a ±20% variation in the output power of the Globar infrared source. b Noise equivalent power (NEP) for the fabricated photodetector at wavelengths ranging from 3 to 20 μm for an optical chopping frequency above 1 kHz. The inset shows the estimated noise current as a function of the gate voltage. All the measurements are carried out at a bias voltage of Vbias = 20 mV