Ultrasensitive Far-Infrared Phototransistors Fabricated in Superlattice Structures

Charge sensitive infrared phototransistors (CSIPs), ultrasensitive detectors in the wavelength range of 10–50 µm, are fabricated in GaAs/AlGaAs superlattice structures. The superlattice structures consist of alternately grown 2-nm-thick Al 0.3 Ga 0.7 As tunnel barriers and thickness-modulated GaAs layers from 2 to 10 nm. The tilted miniband formed in a superlattice structure serves as a potential slope similar to formally used compositionally graded barriers. The utilization of the superlattice in a CSIP is expected to give advantages of easier design, less impurities, and better repeatability in crystal growth, and therefore provides more reliable device performance. The novel structure paves the way for the future mass production of CSIPs.