Surface and Interface States of Ga Compound - Research Paper Example

The paper discusses various issues related to the gallium compound semiconductors including both the interface and the surface properties. It discusses the formation of the surface state and the charges at the interface state when interfaced with various metals. Background Surface state: Intrinsic and extrinsic A considerable number of clean semiconductor surfaces show signs of both intrinsic and extrinsic surface states. Surface states of materials can be defined as the electronic states that are found at the material’s surface.

Surface states are formed as a result of the sharp transition from solid materials that terminates with the surface. Surface states are usually found close to the surface in the atomic layer. The changes of the electronic band structure to vacuum from the bulk materials are caused by the surface material termination. After the termination of the surface material, a weakened potential is created at the surface which leads to the formation of new electronic states know as the surface state [3].

The bands of the solid on the surface of semiconductor crystals get related to vacuum energy since it takes a considerable amount of energy to remove the electrons from the crystal to the vacuum. This due to the fact that the formation of crystal from far separate atoms lower the energy hence the high amount of energy involved in the electron removal. The chemical bonds at the surface of the crystal have their periodic pattern interrupted at the surface which in turn results into unsaturated bonds [1].

After the interruption, the unsaturated bonds then rearrange themselves through surface reconstruction which may be saturated by a layer of atoms. The re-arrangement of the saturated bonds results in changes in both the allowed energies and the surface crystal structure. The formation of surface states can be best described by Bloch’s Theorem which allows the wave vector function to be a complex number. In principle, an imaginary wave vector corresponds to a damped wave function which is exponential in nature.

In perfect finite non physical crystal that does not experience periodicity violation and experiences a translational symmetrical break allowing wave vector with nonzero imaginary components [6]. With the conditions fulfilled, it can therefore be shown that the resulting states are localized at the surface. The energies of the formed states are located at the surface which forms a separate band of surface states. The number of atoms per area at the surface of a crystal greatly determines the number of surface states per area of the crystal.

The number of states can however be compromised of states in the crystal without boundary would have contributed to the conduction bands or the valence bands [5]. In the case of intrinsic semiconductors, the number of filled surface states is equivalent to the number of electrons removed from the bulk valence band due to the change in neutrality. The filled surface states are considered donor like states given that they have electrons that can be donated to the empty available states. Empty surfaces states on the other hand can be considered as acceptor like given that they have empty available surface states which can be occupied by electrons [3].

Intrinsic surface states Intrinsic surface