Herbert Kroemer is a renowned German-American physicist who earned the 2000 Nobel Prize in Physics “for pioneering the use of semiconductor heterostructures in high-speed and optoelectronics.” As a child, he was intelligent and extremely troublesome at school. He avoided expulsion solely due to his academic excellence. After graduating from high school, he studied physics at the University of Jena. However, he fled to West Germany and gained entrance to the University of Göttingen, where he got his Ph.D. at the age of twenty-four. He began his career as a ‘House Theorist’ at the German postal service’s Central Telecommunications Laboratory (FTZ) but quickly began exploring the frequency restrictions of the new transistors, which led to his work on heterostructures. He later worked at RCA Laboratories in New Jersey, Philips in Hamburg, Varian Associates in California, the University of Colorado in Boulder, and the University of California at Santa Barbara. At each location, he conducted research on a variety of semiconductor-related topics. However, it was his work on heterostructures that garnered him the Nobel Prize in Physics and laid the groundwork for tremendous technological advancement.
Childhood & Adolescence
Herbert Kroemer was born on August 25, 1928, in Weimar, Germany, and became a member of the German Democratic Republic following World War II (East Germany). His parents did not graduate from high school. His father worked for the city government, while his mother was a stereotypical German housewife.
Herbert is the eldest of three children born to his parents. Though his parents were illiterate, they were anxious to provide their children with the greatest education possible. His mother was very adamant about it, and she pushed him constantly to earn the highest grade in the class.
He was an exceptional student who excelled in physics, chemistry, and maths. However, young Herbert, like many other intelligent pupils, frequently felt bored and occupied himself by causing disturbances among his peers. Academic excellence saved him from expulsion.
In 1947, he graduated from high school and enrolled at the University of Jena, majoring in physics. Unfortunately, the University came under governmental inspection the next year, and students began to vanish; some fled to West Germany, while others were detained and sent to work in mines.
Kroemer began his career in 1948 as a summer student at the Siemens Company in Berlin. He chose to relocate to West Germany through one of the empty airlift return aircraft as the ‘Berlin airlift’ began. Prior to his departure, he applied for admission to many West German universities but received no response.
When he arrived in West Germany, he was reminded of a request from one of his Jena teachers to express his greetings to Professor König at Göttingen. As a result, he contacted König, who informed him that the physics department had closed admissions.
Nonetheless, he invited him to have a friendly chat with Professor Richard Becker and Dr. Günther Leibfried. In response, they requested that he meet Wolfgang Paul and Robert Pohl. He quickly realized that the academics were evaluating him.
Whatever the reason for these ‘pleasant discussions,’ he eventually gained admission to Göttingen University and found the setting “wonderfully fascinating.” However, he did not have an easy life.
Due to the fact that his father could no longer support him due to the currency exchange rate, he was forced to work night shifts in an aluminum foundry and study during the day. He eventually began working on what became known as band offsets at heterojunctions for his diploma (MS) thesis under Fritz Sauter.
He quickly became fascinated by heterojunctions. He also presented a discussion on John Bardeen and Walter Brattain’s article ‘Physical Principles Involved in Transistor Action’ at some point in the future, and provided some ideas about a few concerns addressed by the authors.
Sauter was ecstatic and instructed him to immediately halt work on his diploma thesis and submit his paper. Although he objected, he followed instructions. Thus, he earned a diploma in theoretical physics in 1951.
Sauter now desired Kroemer to concentrate on his Ph.D. thesis, and Kroemer took his suggestion and began researching hot electron effects in the collector space-charge layer of the then-new transistor. He eventually earned a Ph.D. in 1952.
Herbert Kroemer ‘s Career
Herbert Kroemer began his work as a ‘House Theorist’ at the German postal service’s Central Telecommunications Laboratory (FTZ) shortly after getting his Ph.D. in 1952. His role was to respond to any theoretical questions posed by group members and to deliver a weekly discussion on any topic deemed relevant.
Later in his career, he began researching the frequency constraints of modern transistors, which led to his work on heterostructures. He published his first article on the heterostructure bipolar transistor in 1954.
Later that year, he relocated to the United States of America and began working as a research scientist at the RCA Laboratories in Princeton, New Jersey. He restarted his work on heterostructures and produced two seminal publications during this time.
He defined quasi electric fields in one of them, which he regarded to be the underlying design basis for all heterostructures, in 1957. Regrettably, it lacked appeal.
He soon developed homesickness and returned to Germany in 1957. He then became the Group Leader of Philips Semiconductor Research Group in Hamburg. He was, however, dissatisfied with the work.
As a result of a contact from Varian Associates in Palo Alto, California, he went to America in 1959 and was hired as a Senior Scientist at the institute. He proposed the hypothesis that would earn him the Nobel Prize many years later while working here in 1963.
This was also the year he established that it was possible to generate a steady-state population inversion in a semiconductor diode laser at room temperature by providing a larger energy gap to the outer regions.
Regrettably, the paper was dismissed. Additionally, he was denied funding for additional experimentation. As a result, he spent the following decade studying the Gun effect, which is the oscillation of electrical current flowing through certain semiconducting substances at high frequencies.
He left Varian Associates in 1966 and joined the Semiconductor Research and Development Laboratory as the Head of the New Phenomena Section. He made another career change two years later, in 1968, when he accepted a position as Professor of Electrical Engineering at the University of Colorado at Boulder.
He returned to heterostructure at Colorado University. The early 1970s were devoted to developing the theory of band offsets, which concerns the relative alignment of energy bands in a semiconductor heterojunction.
He joined the University of California, Santa Barbara faculty in 1976 and remained there until his retirement in 2012. He continued his research on band offsets here and devised an experimental approach for determining these energy bands.
He returned to heterostructure bipolar transistor (HBT) research in the late 1970s, a project he began in the early 1950s. He quickly saw that the technological advancements that permitted the invention of the DH laser were also applicable to the development of the HBT and began advocating for it vigorously.
Professor Kroemer stepped down from his position in 2012. He remains, however, a Professor Emeritus at the University of California and continues to study numerous semiconductor subjects.
His Significant Works
Herbert Kroemer is best recognized for his research on bipolar heterostructure transistors (HBP). He released a paper in 1957 describing his concept of quasi electric fields, which became the essential design principle for all heterostructures.
Later that year, he calculated and mathematically demonstrated that heterostructure transistors are superior to conventional transistors, particularly for certain high-frequency applications. This is because, in contrast to the majority of computer chips and semiconductor components, heterostructures are constructed from a variety of materials.
Awards and Accomplishments
Herbert Kroemer received a joint Nobel Prize in Physics in 2000 for “creating semiconductor heterostructures for use in high-speed and optoelectronics.” Zhores I. Alferov and Jack S. Kilby were his co-recipients. Kroemer and Alferov each received a fourth of the prize, while Kilby received the remaining half “for his role in the creation of the integrated circuit.”
Additionally, he has earned various other honors, the most notable of which are the J J Ebers Award (1973) and the IEEE Medal of Honor (2002).
He was elected a Foreign Associate of the National Academy of Engineering in 1997 and a Foreign Associate of the National Academy of Sciences in 2003.
Personal History and Legacies
Professor Kroemer is married to Marie Louise Kroemer, whom he met during his time as a student at Göttingen University. The couple is the parents of five children.
Asteroid 24751, found on 21 September 1992, was named in his honor as Asteroid Kroemer.
Estimated Net worth
Herbert Kroemer is a wealthy physicist who is ranked among the most popular physicists. Herbert Kroemer’s net worth is estimated to be $1.5 million, based on our analysis of Wikipedia, Forbes, and Business Insider.
When Kroemer wanted to pursue advanced studies in physics, his father, who had no prior knowledge of the topic, simply asked him if he could earn a job doing so. He was satisfied when Kroemer promised him that he could always become a gymnasium teacher.
Although he was appointed Professor of Electrical Engineering at the University of Colorado and later at the University of California, he holds just an honorary degree in engineering.