Esaki is a Japanese surname that has no direct synonym as it is a proper noun. However, the term "Esaki diode" refers to a type of diode named after Leo Esaki, a Japanese physicist who discovered it in 1957. Some synonyms that can be associated with the Esaki diode are tunnel diode, resonant tunneling diode (RTD), and backward diode. These terms describe the same type of diode that uses quantum tunneling to allow current to flow through the device. These synonyms are commonly used in electronics engineering and physics.