On the speed and noise performance of direct ion-implanted GaAs MESFETs

A comparison between the noise performance of millimeter wave MESFETs and Hetero-FETs by using a two-dimensional physical simulator

“…3). The obtained dc current and the transconductance of the MESFET are higher than the same quantities of the Hetero-FET because the simulated MESFET has an optimized structure which leads to the best performance (Feng and Lasker [1]) while for the Hetero-FET a better performance can still be expected if both device geometry and doping level are optimized. For example, it has been mentioned that an aspect ratio between 5 and 7 gives the best performance (Shawki and Salmer [9]) while the value which is used in the present simulation is about 3.6.…”

“…The flow chart of the modified two-dimensional Monte-Carlo heterostructure device simulator is shown in fig. 1 [1]). It has to be mentioned that the recessed-gate region is fully included in the simulation because the device characteristics, and in particular the noise performance, are greatly influenced by it (Abou-Elnour and Sch0nemann [8]).…”

“…Recently, it has been mentioned that optimized MESFET structures are able to produce noise figures which are comparable to or even better than the recorded noise performance of Hetero FETs with the same gate-lengths (Feng and Lasker [1] and Feng et al [2]). The average velocity model which has been used by Feng and Lasker [1 ] is not suitable to take into account the non-stationary transport properties in subhalf-micrometer gate length MESFETs and, moreover, the quantization effects in Hetero-FETs.…”

“…The average velocity model which has been used by Feng and Lasker [1 ] is not suitable to take into account the non-stationary transport properties in subhalf-micrometer gate length MESFETs and, moreover, the quantization effects in Hetero-FETs. This makes the accdracy of the calculated results and the validity of the interpretation questionable.…”

n-type ion implantation doping of AlxGa1−xAs (0⩽x⩽0.7)

“…1 In most GaAs MESFET structures Si ion implantation doping is employed to reduce the transistor access resistance in the source and drain regions, to form lightly doped drain ͑LDD͒ regions, or to form the n-type channel. 2,3 In a similar way, n-type ion implantation doping of the Al x Ga 1Ϫx As barrier material in a AlGaAs/GaAs HFET is desirable. To this end, there have been several reports on the properties of Si ion implantation in Al x Ga 1Ϫx As for select Al compositions; however, there has been some disagreement about the activation properties, particularly for high Al-composition material.…”