Interlevel Ge/Si quantum dot infrared photodetector

Abstract

A self-assembled Ge/Si quantum dot interlevel infrared photodetector operating at room temperature and at normal incidence is demonstrated. The spectral response exhibits two peaks in the 58–82 and 132–147 meV energy regions with full width at half maximum linewidths as narrow as 25 meV. The two photocurrent maxima are ascribed to transitions from the hole ground state to the excited states in the dots. The peak detectivity and responsive quantum efficiency are 1.7×108 cm Hz1/2/W and 0.1% for the transition from the ground state to the first excited state and 7×107 cm Hz1/2/W and 0.08% for the transition from the ground state to the second excited state. At large dc bias, a redshift in the transition energies is observed. We argue that the resonance shifts are due to suppression of the depolarization field effect, representing the experimental manifestation of dynamic screening associated with collective electron–electron interaction in the dots.