Direct observation of transferred‐electron effect in GaN

We report the direct observation of transferred‐electron effect in unintentionally doped GaN epilayers grown by metalorganic chemical vapor deposition. The negative differential resistivity (NDR) was observed from the current‐electric field characteristics in GaN using a metal‐semiconductor‐metal (M‐S‐M) system. The threshold field for the onset of NDR was independent of the spacing of M‐S‐M fingers, and was measured to be 1.91×105 V/cm for GaN with an n‐type carrier concentration of 1014 cm−3. This value is very close to the value obtained from theoretical simulation. This observation is an experimental evidence of transferred‐electron effects in GaN, which is important in understanding GaN energy band structure and in the application of Gunn‐effect devices using GaN materials.