The authors combine optical spectroscopic studies and infrared photodetector development to demonstrate the potential of antimony-mediated InAs quantum dot growth for the production of high performance dot-based devices. By depositing 1 ML of gallium antimonide prior to dot growth, the dot density is increased from ∼3×1010 for conventional InAs dots, to ∼6×1010cm−2. Detailed intra- and interband spectroscopic studies show no significant differences in the electron energy level configuration compared with standard InAs∕GaAs dots, while intraband absorption strength is increased. Furthermore, they have implemented this growth technique to produce a quantum dot infrared photodetector with a detectivity of ∼5×1010cmHz1∕2W−1 at 7.5μm (T=77K).

Complementary interband and intraband optical spectroscopic techniques are used to investigate the band structure and carrier relaxation times in technologically important InAs∕InGaAs∕GaAs quantum dot-in-a-well (DWELL) structures. We determine the dot ground to first excited state energies to be 42meV in the conduction band and 18meV in the valence band. Using intraband pump-probe experiments, electron relaxation times from the well states to the dot ground state are measured to be ∼5ps at 10K. Our results provide important parameters for the design and simulation of DWELL-based interband lasers and intraband midinfrared photodetectors.

Influence of rapid thermal annealing on a 30 stack InAs/GaAs quantum dot infrared photodetector J. Appl. Phys. 94, 5283 (2003); 10.1063/1.1609634Effect of the dot size distribution on quantum dot infrared photoresponse and temperature-dependent dark current

We present experimental and theoretical investigations of the bias-dependent spectral shift of the photoresponse in InAs/In x Ga 1−x As quantum-dots-in-a-well structures. Experimental results show that the wavelength response of the transition from the quantum dot ground state to quantum well states can be Stark-shifted by ∼15% by changing the applied bias between −1 V and +1 V. A theoretical model based on the 8-band k • p method fits our experimental data well using realistic dot parameters. We also demonstrate an increase in the operating wavelength and a reduced bias-dependent spectral shift for samples containing dots formed by depositing less InAs during growth.

Two photon absorption processes in InAs∕In01.5Ga0.85As∕GaAs quantum dot-in-a-well photodetectors are studied using free electron laser excitation. Two photon induced, normal incidence photocurrent, observed in the range of 20–30μm, arises from sequential near-resonant two-step transitions involving electron ground to first excited states in the dot, to quantum well final states. We find a two photon absorption coefficient of β∼1×107cm∕GW at 26.5μm (47meV) and 0.8V applied bias. Second-order autocorrelation measurements exhibit two characteristic time constants of ∼3 and ∼40ps. The latter is associated with the intermediate state electron lifetime, whereas the short decay is explained by the involvement of acoustic phonon assisted transitions.