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Master thesis: Optical and electrical study of chlorine doping in ZnSe epilayers and nanowires

May 2nd, 2018


Deterministic chlorine doping of epitaxially grown ZnSe is an important base for modern optically and electrically controlled quantum devices. One example are Cl-doped ZnMgSe/ZnSe/ZnMgSe quantum well heterostructures. Those allow for the realization of efficient single-photon sources that are useful for quantum networks and cryptographic applications. Alternatively, Cl-doped GaAs/ZnSe:Cl core-shell nanowires provide an innovative and sophisticated platform for studying electron-transport on nanoscale towards applications of the nanowires as electrostatically controlled spin qubits for solid state quantum memories. However, both systems require decent quantitative measurement and control of the Cl-donor concentration to tailor the devices to their specific needs. While in simple epitaxially grown semiconductor materials the doping concentration is typically obtained from standard Hall-effect or capacitance-voltage measurements, such all-electrical determination is challenging in small nanostructures such as nanowires or single-photon sources.

Project Description:

The goal of this master project is the determination of the chlorine doping concentration in ZnSe:Cl epilayers and ZnSe:Cl/GaAs core-shell nanowires with different characterization techniques. Starting with the epilayers, standard analysis of the chlorine concentration will be performed by Hall-measurements for calibration of the exact value as a function of the chlorine content. The latter will be also confirmed by secondary ion mass spectroscopy (SIMS) investigations. Then photoluminescence (PL) measurements will be performed on the same samples to calibrate the donor concentration with the intensity of the PL emission. Based on these results theoretical calculations shall be carried out to estimate the required parameter set to apply scattering scanning near field optical microscopy (s-SNOM) as a second versatile tool to confirm the doping concentration especially in nanostructures. Finally s-SNOM technique will be used to quantify the free electron concentration in chlorine doped ZnSe epilayers and GaAs/ZnSe core-shell nanowires.

General Information:

Most parts of the above master project will be conducted in the workgroup of PD Dr Alexander Pawlis at the PGI-9 institute of Forschungszentrum Jülich. This includes the epitaxy of ZnSe epilayers and nanowires, Hall-measurements and PL investigations. The theoretical modelling of application of the s-SNOM technique and corresponding s-SNOM measurements will be supervised by the workgroup of Prof. Dr. Thomas Taubner at the 1st institute of Physics of RWTH Aachen.

Privatdozent Dr. Alexander Pawlis
Peter Grünberg Institut PGI-9, Gebäude 02.11, Raum 205
Tel.Nr.: +49 (0)2461 61 2077