Leaky-mode effects in plasmonic-coupled quantum dot infrared photodetectors

Abstract

The effects of a heavily doped GaAs top contact layer on a plasmonics-integrated InAs quantum dot infrared photodetector (QDIP) are investigated. A metal photonic crystal (MPC), a 100 nm-thick gold film perforated with a 2.5 μm-period, 2-dimensional square hole array, is employed as a plasmonic coupler. The MPC is fabricated on QDIPs with identical structures except for the thickness (0.1 and 1.3 μm) of the top contact layer (doping concentration ∼2 × 1018 cm−3). For the lowest order surface plasma wave (SPW) resonance, the resonance wavelength undergoes a blue shift of 0.27 μm from 8.26 μm, and the responsivity and detectivity drop by ∼50% for the thicker contact layer. These effects are explained by leaky mode characteristics resulting from the free-carrier-reduced dielectric constant in the contact region that impacts the SPW resonance.

Surface plasmon photodetectors and their applications

“…Hole arrays have been integrated with broadband detectors to introduce wavelength and polarisation selectivity, and enhance the responsivity . Integration is achieved by structuring the top or bottom contact of a detector into an array of sub‐wavelength holes.…”

Quantum Dot Detectors with Plasmonic Structures

“…For materials constituting 2D-Au-CHA:DWELL FPA, a Drude model was applied for the dielectric parameters of Au [15] (1.4 times larger scattering frequency than bulk Au to fit the experimental values obtained from Sandia National Laboratory), n-type GaAs [9] (2 × 10 18 cm− 3 ) and lossy aluminium [16] used as 2D-Au-CHA, contact layer and metal ground plane, respectively. Figures 1(b) and 1(c) show that 20 stacks of QD layers were simplified to an effective absorber layer whose n eff and k eff (real and imaginary parts of refractive index in effective absorber) were taken from Ref [9], measured quantum efficiency [17], and spectral photoresponse. The absorption in the active layer (or effective absorber) is only useful to determine how much the response (e.g., photocurrent, responsivity, or SNR) is enhanced with 2D-Au-CHA, i.e., the absorption of other layers is parasitic.…”

“…For a step closer to the next generation of FPAs, we envision that perforated metal film structures [6,7] will improve the performance of FPA by enhancing the coupling to photodetectors via local field engineering, and will enable spectral sensitivity modifications. In regard to the improved performance at certain wavelengths, it is worth pointing out the structural difference between previous perforated metal film integrated front-illuminated single pixel devices [8][9][10] and our back-illuminated device (FPA) [11]. Apart from the pixel linear dimension, it is a distinct difference that there is a metal cladding (composed of a number of metals for ohmic contact and within the read-out integrated circuit) in the FPA between the heavily doped gallium arsenide (GaAs) used as the contact layer and the read-out integrated circuit (i.e., n-type GaAs/QD-absorber/n-type GaAs/metal cladding).…”

MWIR superlattice detectors integrated with substrate side-illuminated plasmonic coupler

“…[22] Since T2SL has a low refractive index and thin layer of that must couple the SPWs to the substrate, we apply a 100nm thick Ge layer as a higher refractive index material between metal and T2SL to bind the SPWs to the interface and enhance absorption in the active layer. A corrugated metal surface (CMS) consisting of 2-D square array of Germanium (Ge) posts covered with a 250nm-thick gold (Au) film, was fabricated on top of a of T2SL MWIR detector with 200 nm thick active region.…”

“…where i, j are the scattering orders of the array [21,22]. Absorption of the SPW in the T2SL provides a solution to maintaining the absorption of a thick T2SL layer while benefiting from the reduced noise of a thin T2SL layer…”