Energy states in InAs–GaAs quantum dots-in-asymmetric-well infrared photodetector structure

We investigated the energy states in InAs–GaAs quantum dot infrared photodetector (QDIP) structure utilizing near-infrared transmission spectroscopy and photoluminescence (PL) spectroscopy, and correlated to the results of intersubband transitions observed in photocurrent (PC) spectrum. The transmission spectrum at room temperature (RT) shows inflections in the 0.9–1.15 eV region due to the interband absorption in the InAs QDs with peaks at 0.96, 1.04, and 1.11 eV. The peak at 0.96 eV, in agreement with the PL data at RT, is clearly the fundamental hh1–e1 absorption of the dot. The two other peaks can be attributed to the hh2–e2 and hh3–e3 inter-band dot absorption. These results show that there are at least two (likely three) bound states in the conduction and valence band of the InAs QDs, respectively. The PC spectrum was observed at 11 K, between 100 and 400 meV of transition energies with a peak at 163 meV, which corresponds to e1–ewell intersubband transition.