Inhomogeneous Broadening in Photocurrent Spectra of DWELL-IP due to Stoichiometric and Geometric Irregularity of QD Assembly

We report a quantum mechanical analysis of photocurrent response and its inhomogeneous broadening in a GaAs/InGaAs/InAs Quantum-Dot-in-a-Well Infrared Photo detector studied and modeled by Green's Function Formalism. Factors that typically contribute to spectral broadening, namely quantum dot geometric dimension variance, and irregular inter-diffusion of Gallium atom from quantum well to binary Incas quantum dot are primarily taken into account for calculating spectral shifting and consequent widening. Required data of size and alloying non-uniformity of QD is taken from STM of a quantum dot reported by Ouattara et. al. Besides, the effect of having a gradient and blurred boundary between individual compounds of DWELL instead of a sharply defined territory as evident from STM image is discussed in terms of peak wavelength shifting and modulation of dark current. We observed a minimal of 10 times widening of spectral maxima in an inhomogeneous assembly of quantum dot compared to that generated by an all-round homogeneous assembly of QD. Our calculation also identifies the size irregularity of QD to be twice as much responsible as stoichiometric irregularity of QD in contributing to the broadening of the spectrum.