Strain effect on intersubband transitions in rolled-up quantum well infrared photodetectors

Pre-strained nanomembranes with four embedded quantum wells (QWs) are rolled up into three-dimensional (3D) tubular QW infrared photodetectors (QWIPs), which are based on the QW intersubband transition (ISBT). A redshift of similar to 0.42 meV in photocurrent response spectra is observed and attributed to two strain contributions due to the rolling of the pre-strained nanomembranes. One is the overall strain that mainly leads to a redshift of similar to 0.5 meV, and the other is the strain gradient which results in a very tiny variation. The blue shift of the photocurrent response spectra with the external bias are also observed as quantum-confined Stark effect (QCSE) in the ISBT.