Surface Electronic Properties of Si‐Doped AlGaN and Thermionic Emission Characteristics with Adsorption of Alkali Metal Atoms

A thermionic energy converter (TEC) is a heat engine with a high theoretical efficiency, but a reduction in operating temperature is required for practical applications. Herein, the experimentally determined thermionic conversion characteristics of Si‐doped GaN films with Cs adsorption at 600 °C are reported. Low‐temperature thermionic emission around 300 °C is also reported for Si‐doped AlGaN surfaces with Cs adsorption. This emission temperature is considerably lower than the operating temperatures of conventional systems with a metal emitter. The AlGaN thin films are grown on n‐type 6H‐SiC substrates, and it is confirmed by ultraviolet photoelectron spectroscopy that the work function decreases as the AlN mole fraction x in the AlGaN samples is increased. Threshold temperatures of thermionic emission decrease with increasing AlN mole fraction and a corresponding reduction in the work function.