June 24, 2007
June 24, 2007
June 27, 2007
Electrical and Computer
12.592.1 - 12.592.8
Electrons, Holes, and the Hall Effect
Many students studying semiconductor theory have a difficult time grasping the concept of a hole as a real particle. From their experience in chemistry, physics, and electrical circuits classes, they have a firm grasp of the electron as a particle. However, the concept of an electron vacancy in the valance energy band of a semiconductor crystal behaving as a positive charge with mass seems metaphysical to them. In order to demonstrate that the theory is based on observations, an undergraduate student built a Hall effect device to measure the Hall effect voltage for doped semiconductor material. The Hall device will be used in future electronics classes as a demonstration of the electron-hole theory of semiconductor material. The project has two main results: the research student learned the laboratory procedures for making Hall effect devices using photolithography and thin film diffusion processes on silicon wafers and the electronics class now has a laboratory demonstration for reinforcing the electron-hole theory of semiconductors.
Our paper will present the difficulties encountered during construction of the Hall effect devices. The primary difficulties in building the devices are finding the correct balance of three factors: the magnetic flux density of the magnetic field, the current flowing through the doped semiconductor, and the sensitivity of our measuring instruments. Stronger magnetic fields and larger currents flowing through the Hall effect device cause the Hall effect voltage to be larger. However, we must balance this against the safety issues of strong magnetic fields and damaging the semiconductor material with too large of a current density. Finally, the paper will present a description of how the Hall effect devices will be used in the classroom to reinforce electron- hole current flow theory.
The purpose of this research project is to build a Hall Effect device to demonstrate different charge carriers of the electrical current flow in p-type and n-type semiconductor materials. The demonstration is to be used in an undergraduate electronics course to prove the existence of hole current flow and electron current flow in semiconductor materials.
Eventually, the demonstration will consist of two Hall Effect devices: one with a p-channel conductor and the other with an n-channel conductor. However, we currently have constructed only the n-channel device. We started with the n-channel device because our laboratory has been doping n-type channels and regions for several years. It is only within the last year that we have obtained equipment to do p-type doping and we expect to create a p-channel Hall Effect device in early 2007.
To briefly explain the concept of this project, consider the atomic levels of semiconductors: elemental semiconductors have four electrons in the outer shell. At absolute zero (0 K) the
Addington, J. S., & Dale, W., & Putnam, I. (2007, June), Electrons, Holes, And The Hall Effect Paper presented at 2007 Annual Conference & Exposition, Honolulu, Hawaii. 10.18260/1-2--2117
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