In this paper, the device characteristics of an InP hot electron transistor with improved gate insulation are reported. The breakdown voltage
of the gate was increased from 0.5 to 2.5V by increasing the distance between the gate and the electron transport region. Consequently,
the appropriate gate bias at which a clear transconductance peak could be observed was applied. The transconductance was increased
from 55 to 130 mS/mm. When the output conductance was reduced, the open circuit voltage gain was about 10.