Normal incidence silicon doped p-type GaAs/AlGaAs quantum-well infrared photodetector on (1 1 1)A substrate

p-type quantum-well infrared photodetectors (QWIPs) demonstrate normal incidence response due to band mixing by utilizing valence band transitions that may break the selection rule limiting n-type QWIPs. Due to even more complicated valence band structure in (1 1 1) orientation, it is interesting to see that the p-type QWIP show both absorption and photocurrent response dominant in normal incidence. The p-type GaAs/AlGaAs QWIP was fabricated on GaAs(1 1 1)A substrate by molecular beam epitaxy (MBE) using silicon as dopant with a measured carrier concentration of 1.4 × 10¹⁸ cm⁻³. The photocurrent spectrum exhibits a peak at a wavelength of 7 μm with a relatively broad peak width (Δλ/λ_p  50%), indicating that the final state is far deep within the continuum of the valence band. The p-QWIP demonstrates a responsivity of about 1 mA/W, which is limited by the relatively low doping concentration.