Clarifying the Differences Between the p/n-Type Definitions Based on Materials and Energy Levels

Understanding the behavior of p-n junctions is fundamental in semiconductor physics and electronics engineering. Traditional teaching methods often focus on material-based definitions of p-type and n-type semiconductors by discussing doping. However, within the depletion region, an additional description is also applicable; this relates to the relative positioning of the energy, which depends on the energy discrepancy between the Fermi (Ef) and intrinsic Fermi (Ei) levels and is also based on carrier type. These two descriptions are at variance when describing the properties of the voltage drop and the energy band bending in the depletion regions of the p-n junction diode in equilibrium, and also when the doping is asymmetrical (Na≠Nd). Our experience teaching introductory semiconductor courses has revealed a lack of clarity regarding the behavior of the region types within the depletion region, which can, in turn, lead to confusion and hinder students’ understanding of the critical concept of voltage drop in the depletion region. This paper aims to underline the difference between the two descriptions above and propose specific terminology for the energy band-based definition in the depletion region; we suggest that instead of “n-type” and “p-type”, the terms “n-like” and “p-like” materials will be used. Further, building on the similarities in energy band bending and potential variations between p-n junctions and MOS capacitors, we suggest that studying the depletion region of p-n junctions can offer valuable insights into the formation and behavior of the inversion layer at the semiconductor surface of MOS capacitors.