Three-band quantum well infrared photodetector using interband and intersubband transitions

Abstract

This paper presents the design, fabrication, and characterization of a quantum well infrared photodetector capable of detecting near infrared (NIR), midwavelength infrared (MWIR), and long wavelength infrared (LWIR) simultaneously. The NIR detection was achieved using interband transition while MWIR and LWIR were based on intersubband transition in the conduction band. The quantum well structure was modeled by solving self-consistently the Schrödinger and Poisson equations with the help of the shooting method. Intersubband absorption in the sample was measured for the MWIR and LWIR using Fourier transform infrared spectroscopy, and the measured peak positions were found at 5.3 and 8.7 μm, respectively, which are within 5% of the theoretical values, indicating the good accuracy of the self-consistent model. The photodetectors were fabricated using a standard photolithography process with exposed middle contacts to allow separate bias and readout of signals from the three wavelength bands. The background limited infrared performance for the LWIR quantum wells shows an upper operating temperature of about 70 K, limiting the overall device. Photocurrent spectroscopy was performed and gave three peaks at 0.84, 5.0, and 8.5 μm wavelengths with approximately 0.5, 0.03, and 0.13 A/W peak responsivities for NIR, MWIR, and LWIR bands, respectively. These results demonstrate the possibility of detection of widely separated wavelength bands, in a single pixel device, using interband and intersubband transitions in quantum wells.