Characterization and performance of a GaAs/Al0.3Ga0.7As quantum-well infrared photodetector

A 200-mu m-diameter quantum-well infrared photodetector with 20 periods of the GaAs(45 Angstrom)/Al0.3Ga0.7As (260 Angstrom) multiple quantum well has been prepared and characterized. The absorption spectrum at 290 K is peaked at 8.78 mu m with a full width at half maximum (FWHM) of 1.42 mu m. The peak changes to 8.36 mu m with a 0.90-mu m FWHM at 10 K. In the photocurrent (PC) spectrum at 80 K, a main peak is observed at 8.34 mu m, and a shoulder peak appears at 7.8 mu m with increasing bias. The FWHM of the main peak in PC spectrum increases from 0.72 mu m to 1.32 mu m as the bias voltage increases from 0 to 2 V. The blackbody responsivity almost linearly increases to 7.4 mA/W at 1 V and then saturates from 1 to 1.8 V, above which it reaches avalanche, while the noise current exhibits avalanche at lower bias than the response does. At 1 V, the optical gain and the quantum efficiency are estimated to be 0.5 and 1.8%, respectively. The peak detectivity of the quantum well infrared photodetector is 2.1 x 10(9) cmHz(1/2)/W.