Investigations in Dark Current and Photoresponse of Doped InAs/GaAs Quantum Dot Photodetector

In recent years, the improvement in specific detectivity (D*) of QDIP can be achieved due to increasing device photorespense or lowering the dark current. The InAs/GaAs QDIP studied in this work belongs to n+-n-n+ structure with single Al0.3Ga0.7As blocking barrier layer and growing on a 45° facet polished GaAs substrate. In the thesis, we have investigated the performance of QDIP with n-doped quantum dot matrix depending on temperature and biasing. The activation energies are not only calculated using the Arrhenius model extracted by temperature-dependent dark current, but also predicted well the exact dark current by the modified 3D carrier drift model under specific temperature operation. The blue-sfhifted photoresponse was also observed under the higher biasing voltage. Due to asymmetric device structure, the profile of photoresponse versus biasing can be obtained. Under the operation temperature of 80 K, the maximum semi-simulated D* remains 9 × 1010 cm Hz1/2/W. The activation energy near zero bias is approached to 250 meV.