Two-dimensional simulation of orientation effects in self-alignedGaAs MESFETs

The stress-induced orientation effects in self-aligned GaAs MESFETs were studied using a two-dimensional analysis. Devices oriented along different crystal directions, with different gate lengths, and under different stress conditions were studied. It was found that the piezoelectric effect caused by the surface stress plays a very important role in the device characteristics of short-channel self-aligned MESFETs. Structure parameters such as lateral spreading of N⁺ ions and p-type impurity concentration in the substrate were found to have great influence on the short-channel effect as well as the orientation effect. The short-channel effects can be suppressed and the device performance improved if the devices are oriented in the right direction and the structure of the devices and the thickness of the surface dielectric layer are properly chosen