Gerd Otto Mueller

Gerd was born on May 2nd, 1931, in Chemnitz, Germany where he also grew up. His mother, Wally Müller was a tailor, and his father, Otto Müller a book setter.

In 1948 he started to study physics and mathematics at Humboldt University in Berlin and received his diploma in Physics in 1953. This year he also began to work at the German Academy of sciences. 1961 Ph.D. of Humboldt University Berlin and 1972 habilitation, 1977 appointment as Professor for Solid State Physics of Academy of Sciences.

The same year he became the head of the Optoelectronics division at the Central Institute for Electron Physics (ZIE), where he worked until 1991. In 1981 he founded a Department of Thin-Film Electroluminescence and supervised and co-supervised over 50 Ph.D. students.

The early nineties were a time of great change. With the dissolution of all Institutes of the Academy of Sciences after the German unification, Gerd’s group was attached to the Heinrich-Hertz Institute for Telecommunications, but here he got fired.

At the time Gerd and Regina were also consulting for several companies across the world. In 1993 at the age of 62 Gerd came to the United States along with Regina to start again.

In July 1994, they joined Hewlett Packard Laboratories working on electroluminescent materials for various device concepts—printer applications, phosphors for digital photography, and scanners and fax machines. Here Gerd started to set up a unique Lab for the characterization of phosphors and GaN LEDs with special attention to high excitation levels. At the same time set up cooperations and consultancy agreements with companies and universities in the US and worldwide (Tottori and Ehemi Uni Japan, Uni Paris, and Bordeaux,…). As a reaction to the invention of blue GaN LEDs and the conversion of the blue emission to white by a phosphor (Nichia) in 1997, a joint position paper on Phosphor-LED devices between Philips Research (in Aachen and Briarcliff) and HP Labs (Gerd and Regina at HP Labs) was put together and the Agilent Labs AGL-2000-1 “White Light Emitting Diodes for illumination” was published.

In 2000 Gerd and Regina joined Lumileds together with their Lab set up from Agilent Labs. Their early experiments resulted in the first 2 phosphor warm white LED products released in 2003. In strong cooperation with Philips Aachen and Uni Munich (LMU), they recognized the potential of applying ceramic phosphors in high-power applications which led to Lumileds firsts in the application of garnet ceramics for white applications as well as nitride ceramic phosphors for pcAmber.

Gerd’s lifelong research focus was the luminescence of materials at high excitations. His skills in experiments and instrumentation, and his thought leadership were key to the demonstration of evidence of Auger recombination as the cause for epi efficiency droop with increasing excitation. The seminal work was published in a highly cited J. Applied Physics Paper in 2007.

While at Lumileds he devised a setup to measure droop in phosphor materials and could separate saturation from quenching. The work on phosphor photo-thermal quenching in Eu-activated nitrides was published in 2016 when Gerd and Regina were already in retirement.

Gerd retired from Lumileds along with Regina in 2009 but stayed highly active in consulting for many companies. He also continued to serve on the Board of editors of physica status solidi (a) for which he was a founding member of the advisory board in 1970 and a member of the Board of Editors from 1981.

Besides his scientific accomplishments, Gerd enjoyed the outdoors, played tennis, and skied the double black diamond slopes until he was 85 years old. All these hobbies they enjoyed together.

Back in Berlin, they liked to sail in the summer months on the many lakes in Mark Brandenburg.

Gerd Mueller is survived by his wife and colleague Regina Mueller-Mach and Regina’s son Clemens Mach

On February 26, 2023, a sea scattering of his ashes into the San Francisco Bay took place