Bound-to-continuum intersubband photoconductivity of self-assembled InAs quantum dots in modulation-doped heterostructures

Abstract

We have designed and fabricated a quantum dot infrared photodetector which utilizes the lateral transport of photoexcited carriers in the modulation-doped AlGaAs/GaAs two-dimensional (2D) channels. A broad photocurrent signal has been observed in the photon energy range of 100–300 meV due to the bound-to-continuum intersubband absorption of normal incidence radiation in the self-assembled InAs quantum dots. A peak responsivity was as high as 4.7 A/W. The high responsivity is realized mainly by a high mobility and a long lifetime of photoexcited carriers in the modulation-doped 2D channels. Furthermore, it is found that the observed photosensitivity survives up to 190 K.

Intraband transitions in quantum dot–superlattice heterostructures

“…Although quantum well structures were already successfully used for infrared (IR) light detection 15 , these structures suffer from their insensitivity to normal light incidence. In contrast, QDs are able to absorb efficiently IR light under normal incidence 16,17,18 , which considerably simplifies the layout of potential photodetectors and sensor applications. Furthermore, QD structures are expected to provide higher photocurrents and lower dark currents than quantum well structures due to the longer lifetime of the excited states 19,20 .…”

Unbound states in quantum heterostructures

“…Besides, the nature of the QD continuum is largely unexplored and it would be useful to know if there are certain energies in these continuums that influence markedly the photoabsorption. In this respect, Lelong et al [50] reported a theoretical analysis of Lee et al data [49] that correlated features of the photo-absorption to the virtual bound states of the QDs. Finally, the link between the QD shape and the nature of the photo-absorption, if any, remains to be elucidated.…”

“…There have been indeed several studies of photo-detectors based on InAs QDs (see e.g., [33][34][35][36][37][38][39][40][41][42][43][44][45][46][47][48][49][50])…”

Excitation power dependence of photoluminescence spectra of GaSb type-II quantum dots in GaAs grown by droplet epitaxy

“…1 Advanced memories and photodetectors using QDs are also proposed, where the carrier population in QDs is varied by external electric fields or optical excitations. [2][3][4] Moreover, self-assembled QDs are expected to be applied for single-photon emitters, entangled two photon sources for quantum cryptograpy, 5 and high-efficiency solar cells. [6][7][8] Although type-I QDs, such as In(Ga)As QDs in GaAs, have received much attention, interest is also growing in type-II QDs which confine only electrons or holes and keep the others outside.…”