Electrical and optical response of a very high frequency AlGaAs/GaAs heterojunction bipolar transistor

Measurement of current gain cutoff frequency in very high frequency AlGaAs/GaAs heterojunction bipolar transistors indicates the existence of cutoff frequencies at 72 ad 84 giga hertz at room and at fixture temperature of 20 Kelvin, respectively. The gain cutoff frequency is measured at 20 and 300 Kelvin by picosecond optoelectronics. Visible optical response of the transistors indicates that the FWHM has a value of 14 and 95 ps at 300 and 20 Kelvin, respectively. Infrared optical response indicates that the FWHM is greater than 50 ps.