Micro- and Macroscale Ideas of Current Among Upper-Division Electrical Engineering Students

The concept of electric current is fundamental in the study of electrical engineering (EE). Students are often exposed to this concept in their daily lives and early in middle school education. Lower-division university courses are usually limited to the study of passive electronic devices and simple electric circuits. Semiconductor physics is an upper-division course that presents the physics behind semiconductor devices in depth and exposes the students to microscale explanations of different types of current, such as drift and diffusion currents. This paper investigates how third-year college students majoring in EE link microscale and macroscale concepts of current, and what misconceptions they reveal after one quarter of advanced instruction in semiconductor physics. The interviewees were posed a problem, based on a distracting device structure that exposed student difficulties in defining current, charges and doping, and the plotting of current-voltage (I-V) characteristics. For example, some students had the naïve idea that current is the flow of a particular type of charge (i.e., only electrons or only holes) or that there is a “spectrum of doping.” Almost all students drew a one-quadrant coordinate system for the I-V curves, which might imply that students think only about positive voltages. These findings can inform further studies to identify and address misconceptions in the important area of semiconductor device physics.