Tunnel current in quantum dot infrared photodetectors

Abstract

Infrared photodetectors have been fabricated based on InAs/GaAs self-assembled quantum dot (QD) layers, with various QD densities and doping levels. Dark currents have been measured as a function of applied bias and temperature. They show a clear activation energy, which decreases as the QD shell filling increases. Its absolute value and dependence on applied bias indicate that electrons tunnel from QD levels into the wetting layer of the next period. Resonant structures in the current–voltage curve and in its first derivative confirm the tunneling through the GaAs barrier. Negative differential resistances are observed in highly doped samples at low temperature.

Deep level centers and their role in photoconductivity transients of InGaAs/GaAs quantum dot chains

“…For example, the WL serves as a channel for carrier exchange between the QDs 6,7 and directly influences the dark current of infrared photodetectors. 8,9 For QD heterostructures grown by molecular beam epitaxy (MBE), the thicknesses of the transition regions between materials become comparable to the sizes of the nanostructures themselves. Electrical and optical properties of such heterostructures therefore become dependent on the ideality of the InGaAs/GaAs interfaces, and their description should take into account a realistic influence of the interface states as well as the quantum confined states.…”

Photo and dark current noise in self-assembled quantum dot infrared photodetectors

“…This implies a stronger confinement in the growth direction compared to the in-plane one, leading to several energy levels in each dot. The intersublevel energies are suitable for long wavelength excitations with a broader infrared spectra compared to QWIPs [7][8][9]. All layers have been grown on a semi-insulating GaAs substrate: an undoped 300 nm GaAs buffer layer, a 760 nm n þ GaAs bottom contact layer, a 5 nm GaAs spacer layer, 50 repeats of self-assembled InAs QD layers separated by 30 nm GaAs barriers and a 400 nm n þ GaAs top contact layer.…”

“…Quantum dot infrared photodetectors have attracted more and more attention in the last years since they are expected to reach higher gains and exhibit lower dark current than QWIPs. Furthermore they are sensitive to normally incident infrared radiation not requiring special optical coupling [1][2][3][4][5][6][7][8][9][10].…”

Temperature dependent responsivity of quantum dot infrared photodetectors

“…The activation energy of the dark current is about 140 meV at low bias and decreases linearly with the increase of voltage. The decrease of the activation energy has been investigated to be from the tunneling process between the QD layers [11]. The low activation energy implies the impact ionization could happen at the high voltage region.…”