Ultra-doped n-type germanium thin films for sensing in the mid-infrared.

Slawomir Prucnal,Roman Boettger,Denny Lang,Shengqiang Zhou,Lars Rebohle,Matthias Voelskow,Wolfgang Skorupa,Lasse Vines,Fang Liu,Manfred Helm,Yonder Berencén,Stefan Andric

doi:10.1038/srep27643

Slawomir Prucnal, Roman Boettger + Show 10 more

Open Access

https://doi.org/10.1038/srep27643

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Abstract

A key milestone for the next generation of high-performance multifunctional microelectronic devices is the monolithic integration of high-mobility materials with Si technology. The use of Ge instead of Si as a basic material in nanoelectronics would need homogeneous p- and n-type doping with high carrier densities. Here we use ion implantation followed by rear side flash-lamp annealing (r-FLA) for the fabrication of heavily doped n-type Ge with high mobility. This approach, in contrast to conventional annealing procedures, leads to the full recrystallization of Ge films and high P activation. In this way single crystalline Ge thin films free of defects with maximum attained carrier concentrations of 2.20 ± 0.11 × 1020 cm−3 and carrier mobilities above 260 cm2/(V·s) were obtained. The obtained ultra-doped Ge films display a room-temperature plasma frequency above 1,850 cm−1, which enables to exploit the plasmonic properties of Ge for sensing in the mid-infrared spectral range.

Highlights

In order to achieve the same temperature within the implanted layer, samples flashed from rear-side were preheated up to 180 °C prior to the flash
After f-flash lamp annealing (FLA) the implanted layer is kept at a temperature above 600 °C for about 2 ms while after r-FLA the implanted layer is at a temperature higher than 600 °C for a much longer time
In order to explain the recrystallization mechanism of an implanted Ge layer during front FLA (f-FLA), the different values of the activation energy and the pre-factor for seed nucleation and solid phase epitaxy as well as the temperature gradient within the amorphous layer and the speed of heat dissipation have to be taken into account[30,31,32,33,34,35,36,37,38]

Summary

Introduction

Single-step ion implantation followed by conventional annealing only allows for n-type doping in Ge in the range of 1–3 × 1019 cm−3. Using millisecond-range flash lamp annealing (FLA) and ion implantation n-type and p-type Ge layers with an active carrier concentration above 6 × 1019 cm−3 and 3 × 1020 cm−3 were reported, respectively[22,23,24].

Results

Conclusion