Characteristics of GaAs/AlGaAs HEMT´s fabricated by X-ray lithography

This paper is about the dc and microwave characterization of the first high electron mobility transistors (HEMT´s) realized using X-ray lithography processing. This full field patterning technology is proposed as a way to produce transistors with sub-200 nm gate lengths and high operating frequency. Fully operational devices are demonstrated and characterized. The dc parameters are determined to be comparable to those obtained on similar devices processed with electron beam lithography. A maximum intrinsic transconductance of 575 mS/mm is obtained. This shows that the X-ray radiation does not cause any significant damage to the substrates and that the process developed is viable. Devices with different geometries were tested at microwave frequencies. A current gain cutoff frequency of 70 GHz is measured for the device with the shortest gate-length whereas a maximum oscillation frequency as high as 105 GHz is measured for devices having the lowest gate resistance