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Quantum Dot Infrared Photodetectors: Photoresponse Enhancement Due to Potential Barriers

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ABSTRACT

Potential barriers around quantum dots (QDs) play a key role in kinetics of photoelectrons. These barriers are always created, when electrons from dopants outside QDs fill the dots. Potential barriers suppress the capture processes of photoelectrons and increase the photoresponse. To directly investigate the effect of potential barriers on photoelectron kinetics, we fabricated several QD structures with different positions of dopants and various levels of doping. The potential barriers as a function of doping and dopant positions have been determined using nextnano3 software. We experimentally investigated the photoresponse to IR radiation as a function of the radiation frequency and voltage bias. We also measured the dark current in these QD structures. Our investigations show that the photoresponse increases ~30 times as the height of potential barriers changes from 30 to 130 meV.

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Normal incidence maximum spectral photoresponse of samples B52–B54 at T = 80 K.
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Figure 4: Normal incidence maximum spectral photoresponse of samples B52–B54 at T = 80 K.

Mentions: Photoresponse spectra of the samples B52, B53, and B54 are shown in Figure 4. Spectra of all these samples have the same position of a maximum at ~335 meV at negative bias voltages 3.2 V for B52, 2 V for B53, and 0.8 V for B54, correspondingly. The photoresponse of B54 is several times bigger than that of B52. Each spectrum exhibits also local maximums on the low-energy tail at ~300 meV and at the high-energy tail at ~380 meV. Full width at half maximum is ~45 meV. Let us note that at low voltages the photoresponse increases exponentially as well as the dark current density (see next paragraph). At high voltages, photoresponse sharply decreases. The same shapes and positions of maximum in the spectra provide strong evidence that QDs in all our structures are nearly identical.


Quantum Dot Infrared Photodetectors: Photoresponse Enhancement Due to Potential Barriers
Normal incidence maximum spectral photoresponse of samples B52–B54 at T = 80 K.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3211266&req=5

Figure 4: Normal incidence maximum spectral photoresponse of samples B52–B54 at T = 80 K.
Mentions: Photoresponse spectra of the samples B52, B53, and B54 are shown in Figure 4. Spectra of all these samples have the same position of a maximum at ~335 meV at negative bias voltages 3.2 V for B52, 2 V for B53, and 0.8 V for B54, correspondingly. The photoresponse of B54 is several times bigger than that of B52. Each spectrum exhibits also local maximums on the low-energy tail at ~300 meV and at the high-energy tail at ~380 meV. Full width at half maximum is ~45 meV. Let us note that at low voltages the photoresponse increases exponentially as well as the dark current density (see next paragraph). At high voltages, photoresponse sharply decreases. The same shapes and positions of maximum in the spectra provide strong evidence that QDs in all our structures are nearly identical.

View Article: PubMed Central - HTML - PubMed

ABSTRACT

Potential barriers around quantum dots (QDs) play a key role in kinetics of photoelectrons. These barriers are always created, when electrons from dopants outside QDs fill the dots. Potential barriers suppress the capture processes of photoelectrons and increase the photoresponse. To directly investigate the effect of potential barriers on photoelectron kinetics, we fabricated several QD structures with different positions of dopants and various levels of doping. The potential barriers as a function of doping and dopant positions have been determined using nextnano3 software. We experimentally investigated the photoresponse to IR radiation as a function of the radiation frequency and voltage bias. We also measured the dark current in these QD structures. Our investigations show that the photoresponse increases ~30 times as the height of potential barriers changes from 30 to 130 meV.

No MeSH data available.