Interlevel Ge/Si quantum dot infrared photodetector

A self-assembled Ge/Si quantum dot interlevel infrared photodetector operat ing at room temperature and at normal incidence is demonstrated. The spectr al 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 pho tocurrent 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 1.7x10(8) cm Hz(1/2)/W and 0.1% for the transition from the ground state to the first excited state and 7x10(7) cm Hz(1/2)/W and 0.08% for the transition from the ground state to the second excited state. At l arge dc bias, a redshift in the transition energies is observed. We argue t hat the resonance shifts are due to suppression of the depolarization field effect, representing the experimental manifestation of dynamic screening a ssociated with collective electron-electron interaction in the dots. (C) 20 01 American Institute of Physics.