Influence of delta-doping on the hole capture probability in Ge/Si quantum dot mid-infrared photodetectors.

Andrew Yakimov,Victor Kirienko,Anatolii Dvurechenskii,Aleksei Bloshkin,Vyacheslav Timofeev

doi:10.1186/1556-276x-9-504

Abstract

We study the effect of delta-doping on the hole capture probability in ten-period p-type Ge quantum dot photodetectors. The boron concentration in the delta-doping layers is varied by either passivation of a sample in a hydrogen plasma or by direct doping during the molecular beam epitaxy. The devices with a lower doping density is found to exhibit a lower capture probability and a higher photoconductive gain. The most pronounced change in the trapping characteristics upon doping is observed at a negative bias polarity when the photoexcited holes move toward the δ-doping plane. The latter result implies that the δ-doping layers are directly involved in the processes of hole capture by the quantum dots.

Highlights

In the past several years, there has been a surge of interest in nanostructures that exhibit quantum confinement in three dimensions, known as quantum dots (QDs)
We present a study of influence of boron delta-doping on the hole capture probability of Ge/Si quantum dot infrared photodetector (QDIP)
As we have demonstrated earlier [12], the photovoltaic dual-peak spectral response centered around 3.4 μm is a direct consequence of a built-in electric field caused by charge redistribution between QDs and δ-doping layers and originates from the hole intraband

Summary

Introduction

In the past several years, there has been a surge of interest in nanostructures that exhibit quantum confinement in three dimensions, known as quantum dots (QDs). The potential advantages of the quantum dot infrared (IR) photodetectors (QDIPs) as compared with twodimensional systems are as follows [1,2]: (i) an increased sensitivity to normally incident radiation as a result of breaking of the polarization selection rules, so eliminating the need for reflectors, gratings, or optocouplers; (ii) an expected large photoconductive gain associated with a reduced capture probability of photoexcited carriers due to suppression of electron-phonon scattering; and (iii) a small thermal generation rate, resulted from a zerodimensional character of the electronic spectrum that renders a much improved signal-to-noise ratio. SiGe-based QDIPs represent another attractive type of the device due to its compatibility with standard Si readout circuitry. The most highly developed technology for fabricating arrays of SiGe-based QDs utilizes strain-driven epitaxy of Ge nanoclusters on Si(001) surface [5]. The photoresponse of p-type Ge/Si heterostructures with QDs in the mid-wave atmospheric window was observed by several groups [6,7,8,9,10,11,12] and attributed to the transitions from the hole states bound in Ge QDs to the continuum states of the Si matrix

Methods

Results

Conclusion