Channeling Effect of Gallium Arsenide (GaAs)

Gallium Arsenide (GaAs) – Channeling Effect

This article explains the channeling effect of Gallium Arsenide (GaAs), and its orientation dependency. The concept of axial channeling is also explained.

The whole concept of crystal orientation becomes important when three main steps are done.

• The etching of the crystal
• Ion-implantation
• Passivation

This introduces an orientation dependency that changes the properties of GaAs field effect transistor accordingly. For example, consider a high energy ion entering a single crystal lattice at a critical angle to the major axis of the GaAs crystal, during ion-implantation. The ion will steer down the open directions of the lattice. This steering is called axial channelling. Thus we can arrive at the conclusion that a random equivalent direction is not used during ion implantation. Thus, the depth distribution will be greater than those predicted by range statistics which are used to establish penetration depth.

The channelling effect is not as high as we think in the <100> direction when compared with <110> direction. Many of the current GaAs wafers tend to take the <100> direction. It should be noted that the profile difference between the aligned <100> direction implant and any other direction of implant has a major influence upon the threshold voltages of the fabricated devices.