Photovoltaic Ge/Si quantum dot detectors operating in the mid-wave atmospheric window (3 to 5 μ m)

Andrew Yakimov,Anatolii Dvurechenskii,Aleksei Bloshkin,Aleksandr Nikiforov,Vyacheslav Timofeev

doi:10.1186/1556-276x-7-494

Abstract

Ge/Si quantum dots fabricated by molecular-beam epitaxy at 500°C are overgrown with Si at different temperatures Tcap, and effect of boron delta doping of Si barriers on the mid-infrared photoresponse was investigated. The photocurrent maximum shifts from 2.3 to 3.9 μm with increasing Tcapfrom 300°C to 750°C. Within the sample set, we examined devices with different positions of the δ-doping layer with respect to the dot plane, different distances between the δ-doping layer and the dot plane d, and different doping densities pB. All detectors show pronounced photovoltaic behavior implying the presence of an internal inversion asymmetry due to the placing dopants in the barriers. The best performance was achieved for the device with Tcap = 600°C, pB = 12 × 1011cm−2, and d = 5 nm in a photovoltaic regime. At a sample temperature of 90 K and no applied bias, a responsivity of 0.83 mA/W and detectivity of 8 × 1010 cm Hz1/2/W at λ = 3.4 μm were measured under normal incidence infrared radiation.

Highlights

In the past years, there has been a surge of interest in structures that exhibit quantum confinement in all three dimensions, commonly known as quantum dots (QDs)
Intersubband optical transitions in QDs have attracted a great deal of attention due to their potential applications in infrared detectors operating at normal incidence and displaying low dark current[1,2]
Ge QDs enclosed in a silicon matrix represent another attractive type of the device due to its compatibility with standard Si readout circuitry

Summary

Introduction

There has been a surge of interest in structures that exhibit quantum confinement in all three dimensions, commonly known as quantum dots (QDs). Intersubband optical transitions in QDs have attracted a great deal of attention due to their potential applications in infrared detectors operating at normal incidence and displaying low dark current[1,2]. Ge QDs enclosed in a silicon matrix represent another attractive type of the device due to its compatibility with standard Si readout circuitry. It has been demonstrated that p-type Ge/Si(001) QDs exhibit intraband photoresponse in the spectral range of 3 to 5 μm[3,4,5,6,7], opening the route towards the fabrication of Si-based QDIPs for mid-infrared atmospheric window. Photovoltaic sensors operating without external bias voltage are preferrable for application in focal plane arrays as they have the advantage of reduced noise

Methods

Results

Conclusion