Effect of external electric field on photo-responsivity of CdS/ZnSe multiple quantum well photodetector

Abstract

We show the enhancement of photo-responsivity through applied external electric field F of CdS/ZnSe multiple quantum well (MQW) photo-detector for the detection of mid infrared wavelengths. The subband energy levels E n are calculated using the Schrödinger equation via finite difference method by incorporating exchange-correlation potential and Hartree potential caused by doping in the well layer. We note that by increasing F , E n and the corresponding optical transition energies decreases. It is observed that dipole matrix element M 21 reduces for higher F and we obtain approximately 38 % lower value of M 21 at F = 40 kV/cm. Moreover, absorption coefficient decreases with F due to the strong dependence on M 21 . We obtain current density of 0.03 A/cm 2 and responsivity of 0.012 A/W at wavelength λ = 2.73 μm for M (number of wells) = 20, well width L w = 2 nm at F = 20 kV/cm. We show that the responsivity is enhanced by increasing M, L w as well as doping concentration N D in the well. We also achieved higher photo-responsivity in CdS/ZnSe MQW using our proposed model as compared to the earlier reported results for GaAs/AlGaAs QWIP . • We achieved enhancement of photo-responsivity in CdS/ZnSe QWIP as a function of electric field ( F ). • The Photocurrent ( J ) and Responsivity ( R ) are more significant at higher F . • Enhnacement of J and R with F is due to the reduction in dipole matrix element. • Increasing doping concentrations, number of wells and well widths of QWIP enhances responsivity.