His PhD thesis was focused on a new physical model describing the switching behavior of narrow base pin diodes. This model was used in the optimization of the efficiency of microwave step recovery multiplier diodes. Results have been partially published in Solid State Electronics vol 32, pp. 593-601, 1989 (A Muller and S Voinigescu "Heavy doping ftfects and stored charge characteristics in narrow base PIN diodes").

Competences
- Silicon, GaAs and GaN micromachining and nanoprocessing, manufacturing of RF MEMS components and circuits, manufacuring of microwave passive membrane supported circuits, micromachined inductors, filters and antennae, monolithically as well as hybrid integrated receiver modules.

- developing acoustic devices (SAWs and FBARs) based on micromachining and nanoprocessing of wide bandgap semiconductors (GaN, AlN). The performances of the SAW and FBAR structures on GaN represent the actual state of the art in the topics. Results were published in IEEE El Dev. Lett. in 2009 and 2010. Dr Muller is now involved in developing of temperature and humidity sensors based on GaN GHz SAW and FBAR structures.

- In the last years Dr. Müller was involved in characterization techniques of microwave semiconductor devices and acoustic devices at cryogenic temperatures (1.5 – 6K) with/without magnetic field and also regarding devices, technology and characterization techniques for the quantum computing domain.

Publications
Dr Muller has published a few tens of papers in high ranked ISI journals like IEEE Electron Dev. Letters, Applied Optics, Thin Film Solids, Appl Phys Lett, Journ. of Micromech. and Microengng, IEEE Trans on MTT, Superlatice & Microstructures etc.. In most of them he was the first author. Dr Muller has more 100 papers in conference proceedings, and has written chapters in books published in Spriger, Francis &Taylor," Editura Academiei" printing houses.

Dr. Muller is reviewer at Elsevier, IoP and IEEE journals.

Dr. Muller is member of PhD Jury in “Politehnica” Univ. Bucharest, Univ. Bucharest and Univ. Paul Sabatier/ LAAS Toulouse.

Long term stages abroad:
- a six month stage in 1991/1992 at IMEC Leven;
- a six month stage at LAAS CNRSToulouse at Director de recherce (2003);

European Projects coordinator:
- coordinator of the the European FP4 „MEMSWAVE” project (1998-2001), one of the first RF-MEMS projects financed by the EC. The project was nominated in 2002 between the 10 finalists for the Descartes prize of the EC. This was the first and for a long time the only EC project in the IST topics coordinated by an Eastern European country.

- coordinator of the FP7 REGPOT- MIMOMEMS (2008 – 2011) “European Centre of Excellence in Microwave, Millimetre Wave and Optical Devices, based on Micro-Electro-Mechanical Systems for Advanced Communication Systems and Sensors”.

- coordinator of the H2020 Marie Curie project “Integrated Crossbar of Microelectromechanical Selectors and Non-Volatile Memory Devices for Neuromorphic Computing” SelectX (2016-2018).

- coordinator of the ESA (European Space Agency) project: Contract No. 40000115202/15/NL/CBi “Microwave filters based on GaN/Si  SAW resonators, operating at frequencies above 5 GHz” (2015-2017).

Dr A Muller was and is the leader of the Romanian team in:
- FP6 NoE AMICOM, 2004-2007, coordinator LAAS Toulouse.
- FP7 Integrated Project NANOTEC, 2011-2015, coordinator Thales TRT.
- FP7 Integrated Project SMARTPOWER, 2011-1016, coordinator Thales TRT.
- FP7 related projects ( ENIAC SE2A (coordinator NXP Semiconductor Netherlands BV), MERCURE (coordinator Thales Research and Technology, France).
- H2020 FETOPEN CHIRON, 2018 – 2021, coordinator IMEC Belgium
- H2020 FETOPEN IQubits, 2019 -2023, coordinator Aarhus Univ. Denmark
HORIZON EUROPE – RIA: „SPIDER” (2022-2025) (coordinated by IMEC, Belgium); „NANOMAT” (2022-2025) (coordinated by Thales TRT, France);
HORIZON EUROPE – EDF: AGAMI EURIGAMI (2022-2025) (coordinated by UMS GmbH, Germany);
HORIZON EUROPE – EDF: POWERFLEX (2022-2025) (coordinated by Thales TRT, France);
HORIZON EUROPE – EDF: POWERPACK (2022-2025) (coordinated by Thales TRT, France).