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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.

No MeSH data available.


AFM images of a typical surface quantum dot sample; different positions on a 2 in. wafer; the deposited In increases from left to right and from top to bottom going from just a wetting layer (left upper image) to a concentration of 4 × 1010 dots/cm2 in the right lower image.
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Figure 2: AFM images of a typical surface quantum dot sample; different positions on a 2 in. wafer; the deposited In increases from left to right and from top to bottom going from just a wetting layer (left upper image) to a concentration of 4 × 1010 dots/cm2 in the right lower image.

Mentions: Typically 10 layers of quantum dots are grown in the active layer of the structure. Also, a layer of InAs dots is grown on the final top surface. All the QDIP structures are grown on n–type doped GaAs epi-ready substrates. Room-temperature images of surface quantum dots taken at ambient conditions by AFM measurements have been used to calibrate and control the quantum dot size and density. A typical AFM result for InAs quantum dots grown on a GaAs surface is shown in Figure 2: the substrate rotation is stopped during the growth of the QDs to get a density distribution over the 2 in. (or 3 in.) wafer. This gives one side of the wafer, closest to the indium source, a higher density of dots and the other side of the wafer, away from the indium source, a lower density of dots.


Quantum Dot Infrared Photodetectors: Photoresponse Enhancement Due to Potential Barriers
AFM images of a typical surface quantum dot sample; different positions on a 2 in. wafer; the deposited In increases from left to right and from top to bottom going from just a wetting layer (left upper image) to a concentration of 4 × 1010 dots/cm2 in the right lower image.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

Figure 2: AFM images of a typical surface quantum dot sample; different positions on a 2 in. wafer; the deposited In increases from left to right and from top to bottom going from just a wetting layer (left upper image) to a concentration of 4 × 1010 dots/cm2 in the right lower image.
Mentions: Typically 10 layers of quantum dots are grown in the active layer of the structure. Also, a layer of InAs dots is grown on the final top surface. All the QDIP structures are grown on n–type doped GaAs epi-ready substrates. Room-temperature images of surface quantum dots taken at ambient conditions by AFM measurements have been used to calibrate and control the quantum dot size and density. A typical AFM result for InAs quantum dots grown on a GaAs surface is shown in Figure 2: the substrate rotation is stopped during the growth of the QDs to get a density distribution over the 2 in. (or 3 in.) wafer. This gives one side of the wafer, closest to the indium source, a higher density of dots and the other side of the wafer, away from the indium source, a lower density of dots.

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.