Responsivity analysis of a resonant cavity QDIP at 10 µm wavelength

In this paper, based on 8-band k.p method, we study the infrared wavelength absorption through the conduction subbands of InAs/GaAs pyramidal shape quantum dots (PSQDs) using finite difference method. Considering homogeneous and inhomogeneous broadening effects we design an asymmetric multiple barrier resonant tunnelling (AMBRT) quantum dot infrared photodetector (QDIP) for lower dark current at lambda=10 mum. Considering coverage factor of QDs, quantum efficiency (QE) of QDIP is calculated. Although absorption coefficient of QDs is large, QE is low due to their ultra short effective absorption region. To enhance QDIP-QE and consequently its responsivity an appropriate resonant cavity structure is proposed. We use InGaAs/InAlAs DBR as the bottom reflector for the designed AMBRT InAs/GaAs QDIP and Au as the top mirror. The reflectivity of the DBR is calculated by transfer matrix method. It is shown that with certain periods of InGaAs/InAlAs DBR, QE increases to about 40 times of similar conventional QDIP.