PRESENTED BYTAIF AIED FAISAL

Design and Analysis of Multicolor QDIP Based on Metallic Nanoslits Array

a new design for a multicolor InAs/GaAs quantum dot (QD) infrared photodetector based on metallic nanoslits array was proposed. The proposed device has an absorption coefficient of more than 50% for designed wavelengths in the infrared (IR) range. the absorption characteristics of the InAs/GaAs QDs affected by metallic nanoslits was analyzed.

Distributed Bragg reflector layers with a buried grating layer are used for enhancement of local field in active layer. The dielectric function of the InAs/GaAs QD layer is calculated by modified Maxwell–Garnett model considering homogeneous and inhomogeneous broadenings, which is then substituted into Maxwell’s equations. Results show absorption enhancement of 100% for certain wavelengths in the IR range, compared with ∼ reference structure.

Introduction

The active layer is stacks of InAs/GaAs QD with 200 nm thickness. There is a HCG layer under the active layer that is utilized for diffraction of incident light. a DBR with six sequential layers is located under the HCG layer. 1000 nm of GaAs layer is considered as substrate. Drude model for Au as a perfect metal is utilized and inserted into Maxwell equations.

STRUCTURE AND NUMERICAL MODEL

The absorption spectrum for reference structure without slit, DBR and HCG layers, is calculated and depicted with S0 legend in Fig. 2(a). Its spectrum shows a wide broadening in mid IR range with absorption peak of about %36. Now we use periodic array of Au metallic nanoslits on the top of S0 structure for efficient interaction with TM incident electromagnetic wave. This new structure is called S0 The guided modes propagating through this structure can be calculated from

where P is period length of slits array and εsub substrate dielectric constant εd is semiconductor dielectric constant, tM is metal thickness and n is number of guided modes.

SIMULATION AND RESULTS

To improve the device performance, a DBR layer is placed under QD active layer in new structure that is called S2

the array of slits with period length of 400 nm, metallic slits width of 320 nm Sub and metal thickness of 400 nm are considered in the structure. For this structure (S1),

To further improve the device performance, we present a new design (S3 structure) in which, one HCG layer is added on the top of DBR layer in Sstructure. This HCG layercauses the incident guided light to be highly diffracted into several beams travelling in different directions.

On the other hand, QDs with advantage of three dimensional confinement can absorb the diffracted light at any propagation angle more than the case of without HCG layer. So it is expected that with adding this layer, absorption coefficient will be increased.

Fig. 4. (a) Absorption coefficient and (b) responsivity of multi-color QDIP based on S1,S2,S3Structures .

1

Electrical field distribution In S1 Structure based device at (a) λ1=2.65µm and (b) λ2=3.76µm

We proposed enhanced QDIP based on array of metallic nanoslits. Using surface plasmon mode excited and coupled to InAs/GaAs QD as active layer, a new metallic nano-slits based structure with DBR and HCG layers was designed. For the designed structure absorption coefficient enhancement of about %100 was achieved in IR range compared to the reference structure. In this analysis, we considered QDs homogenous and inhomogeneous broadenings using MMG model and solved Maxwell equations with FDFD (Finite-difference-frequency-domain) method. Using an appropriate slit array structure, we could design new multi-color QDIP with more than %50 absorption of incident light in each absorbed wavelength.

Conclusion

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